added db abstract class
wired writer.py to abstract DB class
got db plugin to work on write side
added fetch func for webapp integration
finished renaming DB to TSDB
added dependency on graphite-data
Merge remote-tracking branch 'upstream/master'
removed graphitedata dependency and prettied up the diff
fixed bug with exists()
removed unnecessary fetch function from WhisperDB
added commented-out hooks to graphitedata
added commented out plugin config to carbon.conf.example
carbon.conf comment clarification

MAX_CACHE_SIZE unit was not clear.
A bit of cleanup
	Fixed indentation
	Expanded variable names
	Removed unused imports
	Removed extra newlines