SCUBA2: new primitive to determine the config string given to makemap

This primitive searches the history component for the CONFIG parameter
and extracts the following string, returning it in the primitive hash.

Operates only on the file tagged with "newimage" in the current Frame.
general: return the text associated with the given task

This primitive now also returns the text from ndf_hecho for the given
task. The new argument DATA determines whether or not the text is
returned (the default is no). Parsing the history text is left to the
caller.
SCUBA2: store config file and file name in log file

Determine the name of the config file used from the new primitive
_GET_CONFIG_FROM_FILE_ and store that in the log file.