Squashed old stuff :D
Remove unneeded FieldDataEstimator class

Also fixes the wording in a few comments as well as substituting an
assertion instead of an if/else clause.
De-interface-ify MemoryCircuitBreaker
Move MemoryAggregatingCircuitBreaker packages
Move RamAccountingTermsEnum into fielddata package
remove references to field data
Move all the packages
Guuuuuiiiiiice!
Explicitly pass logger to MemoryCircuitBreaker
If a custom postings format is used, wrap the TermsEnum
Make filter settings static strings
Begin removing circuit breaker stats as dedicated stat