[INITIAL] Working version checks

* Check DB structure version, config file version and MPOS core version
* Added new Admin Dashboard to show this core information
* Cronjobs will be disabled if SQL files are not imported
 * SQL files must re-set the db_upgrade_required setting
* Cronjobs will disabled if config files are not updated
 * Simple config file update and version string update will fix this
* Added MPOS status overview
 * Cronjobs and Wallet information for now, others may be added later
* Added new navigation link for Admin Panel Dashboard
* Added new version file
 * Will require updates whenever DB or configs are updated
* Update SQL file that adds the DB_VERSION setting

This will address #1242 and already includes a huge chunk of changes
required to make this work.
[UPDATE] Check for upgrade later
Merge pull request #1246 from TheSerapher/issue-1242

[INITIAL] Working version checks