Add more documentation on how to fork the project, and how to
build on changes using grunt

fix(query editor): Fixed issue with removing query for data sources without collapsable query editors, fixes #4856

allow updates to secureJsonData.

SecureJsonData is stored as a json object in the DB. As the
secureJsonData is never returned to the user they are unable
to provide the full json object when performing updates instead
the user can only provide the specific keys they wish to update.
This commit ensures that only the provided keys are updated and
existing keys in the secureJsonData object are left untouched.

feat(gauge): polish to gauge, better handling of automatic font size, added option to hide threshold markers

closes #4809
closes #4812

add basic Makefile, remove need for global grunt-cli