Abilities added to /user and /sign_in requests

Fix timeout error while showing the network graph.

Fix failure of cheking a merge request after conflict.

Result of misspellings run.

Most of these are comments but a few are strings for users.

Might be an idea to run this from time to time:
https://github.com/lyda/misspell-check

It runs mostly clean now.

Fix Wiki migration task and add more test coverage.

There was an error in the #extract_attributes_from_page method that
caused an exception when checking to see if a page named "Home"
already exists.

The check occurs to handle the renaming of the main index page to
"Home" to match the Gollum standard. If there is already a page
called "Home" then the migrator will leave that page and create
the Index page as usual. Users will need to manually rename their
old "Home" page to something else then rename their "Index" page
to "Home". Fortunately, I would be highly surprised if this case
ever comes up.

I also added more verbosity to the logging so if an error does
occur, it will be easier to track down which Wiki page is causing
the problem.

Adds DB-sensitive tablename escape for backup task.

Update gollum repository location in the Gemfile.

Github just moved the Gollum repository to it's own organization.
This commit updates the Gemfile to point to the new repo location.

I also added a specific ref pointer to a version that is known to
work well just in case they slip up and break their master branch
right at the same time someone happens to be installing or updating
Gitlab. This is about the safest we can get until they put out the
next release that resolves the Pygments dependency issue.