Also, some manual tweaks to fix easy differences between implementation and
interface / related comments:
- make name unique (provided name option is itself unique)
- __name__ property definition is delegated to BaseStorage.__init__
- warn about _is_read_only as being somewhat part of the interface
- make "load"'s "version" mandatory, and assert it is ''
- store: likewise
- registerDB shouldn't require a second argument
- note that tpc_begin doesn't follow interface described behaviour when
  a commit is already running. This is a feature actually, and should be
  harmless to caller.

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2510 71dcc9de-d417-0410-9af5-da40c76e7ee4