[#6759] Replace extra_notes in importers with configurable docs link

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6766] Guess mimetype of imported attachment

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-allura
[#6767] Use .text instead of .string on BeautifulSoup objects

If the element contains no text, .text will return u'' whereas
.string will return None

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
[#5330] Updated version of GitPython to prevent defunct git processes

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>