Simplify category_tree template tag
Simplify category_tree template tag

This commit removes all the custom parsing for what is a basic template tag,
and uses Django's assignment_tag helper instead.
The template tag uses a syntax of '{% category_tree depth={x} ... as ... %}.
To leave the syntax unchanged, I have to rename the keyword parameter
to get_annotated_list to depth. Within the method, max_depth is the better
name, so I explicitly assign it to that. Unfortunately, depth is already
used as a variable name in that method, so I renamed those occurences to
node_depth, which clutters the diff, but should make things less
confusing.

I also removed the cache for the template tag. I see no advantage over
using template fragment caching. Furthermore, we had no mechanism to
invalidate the cache, nor a timeout. I'm surprised this never lead to
complaints, but then looking at the queries, I'm not convinced it worked
as expected either. Either way, KISS. The category_tree template tag
only incurs one query any way.

Just FYI, the tests pass at this point. I'm planning to simplify them in
the next step...

pdonadeo/django-oscar,dongguangming/django-oscar,amirrpp/django-oscar,pasqualguerrero/django-oscar,okfish/django-oscar,Bogh/django-oscar,django-oscar/django-oscar,anentropic/django-oscar,Jannes123/django-oscar,amirrpp/django-oscar,django-oscar/django-oscar,WillisXChen/django-oscar,taedori81/django-oscar,MatthewWilkes/django-oscar,ademuk/django-oscar,lijoantony/django-oscar,sonofatailor/django-oscar,saadatqadri/django-oscar,jlmadurga/django-oscar,sasha0/django-oscar,WadeYuChen/django-oscar,amirrpp/django-oscar,nfletton/django-oscar,eddiep1101/django-oscar,spartonia/django-oscar,bschuon/django-oscar,MatthewWilkes/django-oscar,manevant/django-oscar,kapari/django-oscar,WillisXChen/django-oscar,WillisXChen/django-oscar,WadeYuChen/django-oscar,thechampanurag/django-oscar,kapari/django-oscar,jmt4/django-oscar,ka7eh/django-oscar,jinnykoo/wuyisj.com,kapari/django-oscar,ademuk/django-oscar,jmt4/django-oscar,jmt4/django-oscar,anentropic/django-oscar,binarydud/django-oscar,WillisXChen/django-oscar,mexeniz/django-oscar,jlmadurga/django-oscar,sonofatailor/django-oscar,faratro/django-oscar,rocopartners/django-oscar,dongguangming/django-oscar,monikasulik/django-oscar,john-parton/django-oscar,machtfit/django-oscar,john-parton/django-oscar,michaelkuty/django-oscar,rocopartners/django-oscar,ka7eh/django-oscar,pasqualguerrero/django-oscar,anentropic/django-oscar,saadatqadri/django-oscar,jlmadurga/django-oscar,ademuk/django-oscar,thechampanurag/django-oscar,manevant/django-oscar,nfletton/django-oscar,faratro/django-oscar,amirrpp/django-oscar,dongguangming/django-oscar,sonofatailor/django-oscar,adamend/django-oscar,pasqualguerrero/django-oscar,sonofatailor/django-oscar,Bogh/django-oscar,MatthewWilkes/django-oscar,adamend/django-oscar,solarissmoke/django-oscar,nickpack/django-oscar,Jannes123/django-oscar,itbabu/django-oscar,taedori81/django-oscar,solarissmoke/django-oscar,vovanbo/django-oscar,nfletton/django-oscar,WillisXChen/django-oscar,vovanbo/django-oscar,okfish/django-oscar,mexeniz/django-oscar,eddiep1101/django-oscar,spartonia/django-oscar,pdonadeo/django-oscar,pdonadeo/django-oscar,sasha0/django-oscar,john-parton/django-oscar,QLGu/django-oscar,taedori81/django-oscar,QLGu/django-oscar,spartonia/django-oscar,rocopartners/django-oscar,binarydud/django-oscar,eddiep1101/django-oscar,django-oscar/django-oscar,adamend/django-oscar,sasha0/django-oscar,okfish/django-oscar,faratro/django-oscar,itbabu/django-oscar,michaelkuty/django-oscar,bschuon/django-oscar,anentropic/django-oscar,QLGu/django-oscar,jinnykoo/wuyisj.com,john-parton/django-oscar,monikasulik/django-oscar,eddiep1101/django-oscar,QLGu/django-oscar,vovanbo/django-oscar,solarissmoke/django-oscar,Bogh/django-oscar,jmt4/django-oscar,MatthewWilkes/django-oscar,kapari/django-oscar,itbabu/django-oscar,thechampanurag/django-oscar,bnprk/django-oscar,manevant/django-oscar,bnprk/django-oscar,michaelkuty/django-oscar,nickpack/django-oscar,michaelkuty/django-oscar,nfletton/django-oscar,bschuon/django-oscar,dongguangming/django-oscar,bnprk/django-oscar,Jannes123/django-oscar,ka7eh/django-oscar,WadeYuChen/django-oscar,nickpack/django-oscar,monikasulik/django-oscar,Bogh/django-oscar,jlmadurga/django-oscar,vovanbo/django-oscar,mexeniz/django-oscar,lijoantony/django-oscar,machtfit/django-oscar,pdonadeo/django-oscar,saadatqadri/django-oscar,bschuon/django-oscar,rocopartners/django-oscar,Jannes123/django-oscar,monikasulik/django-oscar,sasha0/django-oscar,WadeYuChen/django-oscar,pasqualguerrero/django-oscar,WillisXChen/django-oscar,jinnykoo/wuyisj.com,machtfit/django-oscar,manevant/django-oscar,thechampanurag/django-oscar,okfish/django-oscar,jinnykoo/wuyisj.com,ka7eh/django-oscar,faratro/django-oscar,mexeniz/django-oscar,itbabu/django-oscar,spartonia/django-oscar,adamend/django-oscar,bnprk/django-oscar,django-oscar/django-oscar,saadatqadri/django-oscar,taedori81/django-oscar,solarissmoke/django-oscar,nickpack/django-oscar,lijoantony/django-oscar,binarydud/django-oscar,lijoantony/django-oscar,ademuk/django-oscar,binarydud/django-oscar