adds caching to normal placeholders and optimizes imports for debugtoolbar cache panel
fixed tests
docs
cache views
Merge branch 'develop' into fix-2267

Conflicts:
	cms/tests/admin.py
	cms/views.py
caching for views.py
docs
do not cache pages for logged in users
test caching of placeholders
page cache finalized, settings added, docs and release notes
Merge branch 'develop' into fix-2267

Conflicts:
	docs/upgrade/3.0.rst
fixed tests
encode path as utf-8
removed import
docs whitespace
docs
Merge branch 'develop' into fix-2267

Conflicts:
	cms/context_processors.py
	cms/tests/views.py
Merge pull request #2687 from digi604/fix-2267

optimizes caching