Configurator: Log unhandled exceptions
MetaService: Publish empty strings instead of null over Zeroconf

This fixes a NullReferenceException in DataFromTXTRecordDictionary.
WSS: Reload MediaInfo when the source file changes
WSS: Improve error handling in XmlCache

Also rename the cache file, as we use a new format now. This avoids a logged exceptions
for all people who upgrade from the previous version.
Configurator: Disallow creating duplicate usernames
Configurator: Fix crash when there are duplicate accounts
MPTVSeries: Fix wrong id returned from episode search
Merge branch 'alternative-mediainfo-fix' into release-0.5
WebMP: Hide system information when loading it fails (fixes #375)

This avoids showing a system with not-operational performance counters as
idle, and also reduces the number of bugreports: nobody will notice it doesn't
work. It's not an important feature anyway.
WSS: Also log ffmpeg path when image extraction fails
WSS: Don't crash when ImageCache.Invalidate() fails
PowerScheduler: Fix returned value when service cannot be connected

The log message in the line above read returning false, and then we return
true. Good job...
Merge branch 'release-0.5'

Conflicts:
	Services/MPExtended.Services.StreamingService/Code/Images.cs
	Services/MPExtended.Services.StreamingService/MediaInfo/MediaInfoWrapper.cs
StreamCopy: Update code style and add AsyncStreamRead() method
Log: Add method to check whether a log-level is enabled
WSS: Log ffmpeg.exe output in ExtractImage to trace-level
Log: Add option to enable trace-level logging to log file
WSS: Run ffmpeg.exe for image extraction as impersonation user for network drives

When the source files are on a network drive, we need to run ffmpeg.exe as a user with
access to that network drive.

Thanks to Shukuyen for endless debugging on this issue.
Merge branch 'extractimage-network-and-log-master'
Library: Create a NetworkContext API for impersonation

- Create an INetworkContext interface which contains network context related
  methods, such as RewritePath()
- Create a dummy and impersonating INetworkContext implementation
- Create a factory for creating INetworkContext instances