Fix db upgrade script and prepare 3.1.0 release (opensourcepos#1242)

Update WHATS_NEW.txt with 3.0.2 improvements

Fix upload path in docker cloud setup

Remove deleted stock locations from low inventory report (opensourcep…

…os#916)

Release files update

Update changelog for 2.3.4

Cleanup migration script, mostly working now (opensourcepos#262)

Fix report generation regression

Version 2.3.1 release

Update README and WHATS NEW