Allow hbase table prefix to be configurable at run-time

[hcoyote]

In our HBase environment, we namespace tables in order to group them and more easily identify which project they're associated with.

Currently, the table names are hardcoded in ./hraven-core/src/main/java/com/twitter/hraven/Constants.java unless you set IS_DEV (which sets PREFIX to "dev.") or you just override what PREFIX is set to. Both options require rebuilding hraven.

It would be great if this were a run-time option that could be set without having to rebuild.

[vrushalic]

Agreed that this will be a good enhancement. The table names in hRaven/hBase should be configurable such that they can be changed at runtime without having to rebuild or redeploy hRaven