Mirror  Logic & File Watcher Buffer

Change to the mirror logic to:

*Always go to the mirror if the mirror is hosted on the same machine as this feed
*Configuration value ("alwaysCheckMirror") to forcefully make it always check the mirror feed

Change to File Watcher:

*Backout the increased buffer size, further reading has shown increasing the size is not recommended as that memory is expensive.
*Add an error handler to firstly log that the watcher has had an error
*Additionally, when there is an InternalBufferOverflowException it triggers the indexer to do a full syncronise with the file system. - this should prevent files which have fallen off the buffer being missed.

(Apologies for getting the file watcher wrong on yesterdays request!)