don't get collection status on instantiation

It's probably better to make this manual; it causes slowdowns
when loading lists of collections.
added file.json_path_rel attribute
add paths to JSON, EAD, METS templates to configs
collection,entity dump_json() can now generate templates

Rather than keeping new collection.json and entity.json template
files laying around (violates DRY, as data is in MODEL_FIELDS),
modify the collection and entity dump_json() functions to generate
fresh JSON files based on MODEL_FIELDS if instructed to do so.
This mirrors functionality in DDRFile.
refactor add_file task, coll/entity create to use new commands

ddr-cmdln commands were modified to take lists of updated files
and lists of (JSON,XML) template files.
This is a step towards moving JSON and XML template files from
lower levels of the stack to this level.
added JSON,XML templates and code from ddr-cmdln

JSON and XML metadata files that are best handled in this layer
of the stack were being managed by ddr-cmdln.  This change moves
the rest of that code into this layer of the stack, along with
the EAD and METS template files.
make sure file.json_path_rel doesn't have leading slashes

This is a relative path so it should not start with a slash.
move entity_annex_add out of try block so errs propagate better

This way the celery task will print actual errors to the logs.
Merge branch 'master' into 075-layer-separation