extract hardcoded api key, fixed ecf files, added a test ecf target, changed ASANA.last_error design, fixed project creation

- extract hardcoded api key and now pass it when creating ASANA object
- removed usage of once, the once are not necessary since the ASANA object is already the main container for asana related data.
- updated ecf files and added a test target
- changed ASANA.last_error design, to be detachable, and being precised only when an error really occurred, otherwise check the is_success: BOOLEAN query.
- fixed ASANA.new_project implementation.
- updated tests to avoid deleting existing tasks from real account.