Added AzureTableBrain

Added Azure Table Storage Brain implementation (and remove rogue
AzureStorageBlobCache, which was an aborted attempt to implement an
Akavache Azure demon hybrid).

Sample mmbot.ini, assuming you have MMBot.AzuteTableBrain.dll and
relevant Azure storage assemblies:

[BRAIN]
NAME = AzureTableBrain

[AZURETABLEBRAIN]
STORAGE_ACCOUNT_NAME = mystorageaccountname
ACCESS_KEY = mysecretazurekeywhichisreallylongandsupersecret===