Allow some activities/graphs to just be executed on the thormaster

Currently there are various operations which cannot be executed in thor - e.g., fileservices functions that require access to dali.

This requires NOTHOR to be added in various non obvious places. A better solution would be to specify that particular graphs should be executed on the master. If this also supported the global file services functions then it may remove the need for NOTHOR altogether.

Likely to need code generator and engine support.