Initial commit, incl Makefiles
Preliminary design of workflow engine. Overview.
New modules and behaviours (placeholders). Updated Makefile to make behaviours before other modules and separated the dialyzer path from making the modules.
wf_date: utility for timestamps and dates. Use wf_date:timestamp() to generate an internal timestamp. Use the various functions to convert the timestamp into a standardized printable date (according to RFC3339).
Simple strawman versions, intended to work at a basic level but not tested yet.