Submodule GitExtensionsDoc updated

Submodule GitExtensionsDoc:
    > 2b99b9a - Revision Links. Closes #51.
    > 0a014fb - Updated build server integration description.
    > 1efb0ad - Add 'quick search' and 'go to commit' to Browse Repository
    > ace7cce - Minor corrections to Browse Repository
    > 5af2f5f - Update settings.png.
    > 492d385 - Add documentation for Build server integration settings.