Fixed #21560 -- missing 'slug' field in example code
I updated the documentation, that the modelform now includes the 'slug' field.
Merge pull request #2058 from c-schmitt/fixes_21560

Fixed #21560 -- missing 'slug' field in example code
Fixed E124 pep8 warnings.
Moved imports to the top of the defaultfilters module.
Fixed #4282 -- stratproject should honor umask
Currently I updated the old patch that it works under python2 and python3.
Also I added a test suite that checks if a file has a mode of 0600 and a directory has a mode of 0700 if i set the umask to 0o077