Fixed warnings when building the documentation.
Fixed #21741 -- Fixed render_to_string to stop pushing empty dictionaries to its Context

Thanks to kezabelle for the report and original patch
and to numerodix for his improved patch.
Fixed #22113 -- changed object_name to model_name in CBV docs.

Thanks to trac user nikunj.sg for the report.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	tests/template_tests/test_loaders.py