bem remove command

[bariscicek]

bem-tools should have a functionality to remove entities in bem tree.
Proposed command should remove entities using the same options as the bem create command.

bem remove --level level1 block__elem_mod 

kind of usage should also work.

Removed entities should be moved to .attic directory on the root of level dir for backup. --force should remove the entity without moving to .attic. Restoring from backup should be a manual work.

bem remove --purge 

should remove the .attic directory of all levels. If level specified only specific level is cleared.