Support issue referencing from Wiki page commit messages

Allow issue linking between wiki page commits and repository issues

Currently any commit message entered for a wiki page doesn't allow you to reference any issues in the repository. Supporting linking would enable issues to be raised for out of date pages etc to be raised and their changes tracked fully.

Linking the Wiki pages to the issues is also consistent with the Gitlab Tutorial - It's All Connected page for linking commits to issues etc.

Nomenclature

Linking a wiki commit to an issue would take the same form, using # to link the wiki commit to issue.