beginnings of #86
working version with meta switch hard coded.

Debug code still present.
Updated documentation.
Added message for when no metadata is found for a file.
tidied up logic.
Will now parse multiple files for metadata

Previously dropped out if one file was missing metadata.
Solves part 1 of metomi/rose#86.
Part 2 of metomi/rose#86.
Merge remote branch 'upstream/master' into 86
Removed code out to function.
Exit on not finding a meta-key value.
Logic tweaks and tidy.
Changed print to stderr call.
Slightly tidier version of making error message up.
Merge pull request #313 from arjclark/86

rose config: meta and meta-key options
closes #86