* split journaldb commit into two functions: journal_under and mark_canonical
* use new commit mechanism in client
* Configurable history size in master
* Reduce DB history
* Configurable history size
* Set min history size
* Test
* Fixed a test and reduced the limit
* Actually enable fat db, and do RPCs for it.
* Implement HashDB traits for AccountDB.
* user defaults
* finished user defaults
* user defaults are network-dependent
* added tests for newly added functions, logger is initialized first
* dir cleanup in progress
* user_file is placed next to snapshots
* fixing requested change