add existing path variable to scope

use existing variable instead of concating strings
refresh() fix

create mm_util.get_default_metadata_data() and
mm_util.get_child_metadata_data() to load metadata JSON centrally,
replace references in the project to the file name.

update to mm_project.refresh() to not bomb out if the metadata item
can't be found for a directory, if the directory is the project root or
/src add all metadata types to the refresh.