Fix key already exists bug.
Merge pull request #1798 from vbjay/Portable

Fix key already exists bug.
Fix for #1790.
Submodule GitExtensionsDoc updated

Submodule GitExtensionsDoc:
    > 18d4200 - Change information about where settings are stored.
    < 439e4cb - add section about re-taggin
Update checked property when menu is shown.  This allows the item to be refreshed between instances.
Merge branch 'Portable'
Merge branch 'pr/n1799_vbjay'
Fixed submodule status on diff tab