Bump version number to 0.5.4
FSPictures: Disable MPPictureShares plugin when configuration is invalid

This avoids an ugly exception in the logs.
WebMP: Don't try to read enableIPv6 property

The enableIPv6 switch in NetworkInformation is a bad idea, but removing it now
will probably break more than it'll fix, so let's use avoid usage in release-0.5 for now.
Drop enableIPv6 flag (closes #397)

Adding the flag just caused more complicated code and occasional bugs
when WebMP tried to use it. Has never been a good idea to make this a
configuration option, especially since we don't offer a GUI setting to change
it.
Configuration: Fix updating StreamingProfiles.xml due to already existing file

Also keep a backup copy of the original file.
Merge tag 'v0.5.4'

MPExtended v0.5.4

Conflicts:
	GlobalVersion.cs