Maya: AssetManager: 1. Made alembic_path attr. on ShotMetadata nodes optional. It is only used when it is set. If it is empty, the alembic path is built from the PIPELINE_ALEMBIC_PATH and the shot_name attr. (THIS IS THE DEFAULT). 2. Added table_view_editor_pathpicker as table view editor for the shot_name. 3. Alembics are now exported into the sub-directories cameras, props and chars. base_data_check() fails if those directories dont exist. 4. Added multi commit for selected items for prop view. Exposed under Selection in context menu of prop_view.