Exception hierarchy

[dan-hook]

Exceptions are currently handled horribly. Mostly they are logged as a warning and processing continues as if they never happened. I'm currently working on a temporary solution, but we need to consider an exception hierarchy to go with the class hierarchy. For starters:

• Create a DatabaseConnectionException that will be thrown when an Accumulo operator class catches an exception from AccumuloException.
• Create a TableException error that will be thrown by D4MInserterIF
• Map MutationsRejectedException and TableNotFoundException in AccumuloInserter to the TableException