Finish support for Pig 0.12

Pig 0.12.0 has added several new keywords such as "Assert" or "In" (via PIG-3367 and PIG-3269). This is causing issues to DataFu UDFs with the same name. I wasn't able to find any other solution other then renaming the UDFs in question. I do understand that this is very intrusive change, so I've provided deprecated ones for backward compatibility - e.g users on Pig 0.11.0 will still be able to use the Assert or In as they are now.

After applying this final set of changes I was able to run all unit tests against Pig 0.12.0 without any issues!