Adds initial GeoNetwork harvester service calls.

Adds harvester 'status' check.
Changes formatting to PEP8 for parts of code.
Adds geonetwork config to extern.yml
Adds harvester creation to service

Only GeoPortal (geoPREST) harvester type supported
Partial implementation of resetharvester
Refactors harvester XML builder
Modifies RR parameter usage.
Adds remaining harvester functionality for M057

Adds remove, run, start and stop commands
Adds ogcwxs (SOS) harvester type
Merge pull request #18 from oceanzus/m057_harvester

Adds M057 GeoNetwork harvester service calls