Added some completion convenience methods to AbstractCommand
ConfigurationManager: add item description API
AbstractCommand: added config completion convenience methods
Configuration validation now much smarter (API breakage)
onConfigurationValidate() now gets the processed value, not the raw 
string value.  old value is also passed.
Prefix handling also handled a bit smarter now.
removed unwanted stuff
Merge branch 'master' of github.com:desht/dhutils