Cleanup, MISP health tool

- cleanup of a lot of deprecated settings
- tool to help assess and alter issues with the instance settings
- new mechanism to store settings
Reworked the server settings for boolean settings and settings that have a few options as values.

- Toggles instead of free-text
Default config.php added
Several changes for the diagnostic tool

- Added extra diagnostic tools
Added the new server settings to the menues
Download of the settings/diagnostics results implemented

- Should help with trouble shooting, administrators can now download a json file containing all the settings and issues shown by the tool.
No feedback from the failed numeric test for incorrect server settings
First small changes to the INSTALL.txt, more to follow before 2.3.0 is ready
Merge branch 'feature/health' into develop