GEOMESA-202, GEOMESA-229 Consolidate unit tests, Re-enable FilterTester Tests

GEOMESA-202: Found areas where Mock Accumulo instances could be shared between tests,
merged some of the separate Iterator tests into the MultiIteratorTest,
added @jnh5y's indexSchemaFormat suggestion to most test DataStore params,
and cleaned up some specs2 code style. All changes should save about
 30 secs in complete build time.

GEOMESA-229: FilterTester was using the same datastore and tables from the AccumuloDataStoreTest,
so it was querying on the wrong features. Now, it gets its own datastore and queries
on the correct features.
I think we prefer to line up arrows:

```
val ds = {
DataStoreFinder.getDataStore(Map(
  "instanceId"        -> "mycloud",
  "zookeepers"        -> "zoo1:2181,zoo2:2181,zoo3:2181",
  "user"              -> "myuser",
  "password"          -> "mypassword",
  "auths"             -> "A,B,C",
  "tableName"         -> "filtertester",
  "useMock"           -> "true",
  "indexSchemaFormat" -> testIndexSchemaFormat,
  "featureEncoding"   -> "avro")).asInstanceOf[AccumuloDataStore]
}
```