Fixed MemoryCacheClient to incr/dec by supplied value

Fixed MemoryCacheClient to incr/dec by supplied value rather than 1/-1
Mismatched version of DotNetAuth causing xbuild errors
Merge remote-tracking branch 'upstream/master'
MemoryCacheClient decrement by amount * -1
Merge pull request #761 from DveMac/master

Fixed MemoryCacheClient to incr/dec by supplied value & Mismatched version of DotNetAuth causing xbuild errors