[cage] run make docs only for installable, add docs-clean to help
[cage] run make docs only for installable, add docs-clean to help

docs with all was too noisy

tkob/parrot,tkob/parrot,FROGGS/parrot,tkob/parrot,tkob/parrot,parrot/parrot,youprofit/parrot,youprofit/parrot,tkob/parrot,FROGGS/parrot,FROGGS/parrot,FROGGS/parrot,tkob/parrot,FROGGS/parrot,tkob/parrot,parrot/parrot,FROGGS/parrot,youprofit/parrot,youprofit/parrot,youprofit/parrot,tkob/parrot,FROGGS/parrot,youprofit/parrot,FROGGS/parrot,youprofit/parrot,parrot/parrot,parrot/parrot,youprofit/parrot,parrot/parrot