Accumulo Mini Cluster for local integration testing

There is no 1.4 branch for this... mini cluster doesn't exist in 1.4.

The mini cluster is a new module, but is not added to the parent pom so that it doesn't get built automatically.
As a potential Scala trick/feature, it might be worth making these two var Options, lazy vals instead.  
```
lazy val dataStoreOption =  { ... Code to get a dataStore ... }
```
The really cool part is that if the idea is for users to call for a dataStore manually in the Scala REPL, it'll be constructed once on demand.  

This does give the possibility that some could create, but not initialize/start a MC and screw things up.  I'm willing to take that risk;)