issue_23: display git hash of current version in the bottom toolbar. Or hide it if its not a git repo

Conflicts:
	crits/core/templates/base.html
Made display of current git hash more efficiently done.
Slight style changes. Moved git_repo_url to be a user inputted field in the control panel view
Removed seperate git hash section from bottom toolbar
Removed ISPROD. Changed link to take you to current commit. Slight style change.

Conflicts:
	crits/core/static/css/core.css
Merge remote-tracking branch 'crits/master' into release_version_pub

Conflicts:
	crits/config/forms.py
	crits/core/templates/base.html
Fixed error caused by overlooked merge conflict
Redo of class_mapper_fixes branch.

Instead of litering try/except blocks in class_from_value() just check
if the type is one we need an ObjectId for and make sure the value is
a valid ObjectId. Makes this easier to read at a glance.

Instead of a giant try/except block in class_from_id() just check up
front for a valid ObjectId. In this case we do not need to check the
type as all queries are done by ObjectId in this function.

Suggested by: dsnellgrove
Discussed in #213.
Encode bucket list item link.

Closes #207.
Ensure is_valid() behaves properly.

Suggested by: dsnellgrove
Merge pull request #216 from crits/class_fixes2

Redo of class_mapper_fixes branch.
Merge branch 'master' into pr/215

Conflicts:
	crits/core/static/css/core.css
Setting up commit for stable version.