Submodule GitExtensionsDoc updated.

Submodule GitExtensionsDoc:
    > 39a232c - In version 2.45 settings are still stored in registry.
    > 7a3ee01 - Chapter 2 Updated
    > 9f1dbdb - Add logo to RTD and release # to TOC
    > d02d225 - Add Wiki details
    > a120c4e - Fix incomplete sentence.
Warning
Autopull from remote to which push was rejected.
Modified minimum size
Disabled autopull for not handled cases. Closes #1887.
Merge pull request #1943 from Itori/master

Fix minimum size on Archive form
Don't write internal nbug log to disk as it tries to write to location that it may not have access to. Closes #1581.
Push rejected error message format has changed.
Add support for installing GitPlugin in VS2013