Move pure tree-related methods of PageQuerySet into a separate TreeQuerySet class
Move pure tree-related methods of PageQuerySet into a separate TreeQuerySet class

This allows them to be re-used on other treebeard.mp_tree-based models.

jnns/wagtail,kurtrwall/wagtail,mikedingjan/wagtail,iansprice/wagtail,hamsterbacke23/wagtail,gasman/wagtail,nilnvoid/wagtail,gogobook/wagtail,Tivix/wagtail,gasman/wagtail,kaedroho/wagtail,rsalmaso/wagtail,takeflight/wagtail,thenewguy/wagtail,chrxr/wagtail,jnns/wagtail,nimasmi/wagtail,serzans/wagtail,timorieber/wagtail,serzans/wagtail,kurtw/wagtail,FlipperPA/wagtail,quru/wagtail,thenewguy/wagtail,zerolab/wagtail,iansprice/wagtail,nutztherookie/wagtail,kurtw/wagtail,jnns/wagtail,zerolab/wagtail,timorieber/wagtail,wagtail/wagtail,gasman/wagtail,kaedroho/wagtail,JoshBarr/wagtail,kurtrwall/wagtail,mixxorz/wagtail,timorieber/wagtail,hamsterbacke23/wagtail,inonit/wagtail,jnns/wagtail,nutztherookie/wagtail,kurtrwall/wagtail,iansprice/wagtail,chrxr/wagtail,inonit/wagtail,gogobook/wagtail,takeflight/wagtail,wagtail/wagtail,serzans/wagtail,nilnvoid/wagtail,davecranwell/wagtail,serzans/wagtail,torchbox/wagtail,gogobook/wagtail,kurtrwall/wagtail,iansprice/wagtail,mikedingjan/wagtail,torchbox/wagtail,Toshakins/wagtail,rsalmaso/wagtail,Toshakins/wagtail,takeflight/wagtail,kurtw/wagtail,mixxorz/wagtail,kaedroho/wagtail,hamsterbacke23/wagtail,takeflight/wagtail,davecranwell/wagtail,torchbox/wagtail,Toshakins/wagtail,nealtodd/wagtail,mixxorz/wagtail,wagtail/wagtail,inonit/wagtail,mixxorz/wagtail,thenewguy/wagtail,FlipperPA/wagtail,thenewguy/wagtail,chrxr/wagtail,timorieber/wagtail,JoshBarr/wagtail,quru/wagtail,gogobook/wagtail,davecranwell/wagtail,hamsterbacke23/wagtail,torchbox/wagtail,kurtw/wagtail,rsalmaso/wagtail,quru/wagtail,JoshBarr/wagtail,nutztherookie/wagtail,Tivix/wagtail,rsalmaso/wagtail,Tivix/wagtail,mixxorz/wagtail,nutztherookie/wagtail,mikedingjan/wagtail,nimasmi/wagtail,zerolab/wagtail,nealtodd/wagtail,Tivix/wagtail,wagtail/wagtail,nilnvoid/wagtail,JoshBarr/wagtail,Toshakins/wagtail,nilnvoid/wagtail,kaedroho/wagtail,gasman/wagtail,zerolab/wagtail,thenewguy/wagtail,davecranwell/wagtail,nimasmi/wagtail,zerolab/wagtail,nimasmi/wagtail,nealtodd/wagtail,quru/wagtail,inonit/wagtail,FlipperPA/wagtail,mikedingjan/wagtail,FlipperPA/wagtail,gasman/wagtail,kaedroho/wagtail,nealtodd/wagtail,chrxr/wagtail,rsalmaso/wagtail,wagtail/wagtail