Fix #1317: remove Bower from Makefile
Fix #1317: remove Bower from Makefile

Some Bower-dependant commands were switched to Yarn; additionally,
a `clean` command was updated to not clean application DB, but
remove all testing DBs.

pbanaszkiewicz/amy,swcarpentry/amy,pbanaszkiewicz/amy,swcarpentry/amy,swcarpentry/amy,pbanaszkiewicz/amy