Moving to Endevver standard plugin layout
Support `$app->query`
Use the more succinct `$app->errtrans`
MT version checking to conditionally run `ajax_login` code

It would be hell to try to integrate the MT4 and MT5 versions, so I'm simply creating a separate subroutine entirely.
Introduction of MT 5 compatible code: `_ajax_login_mt5`
Fixed a few return values and reverted stylistic changes for easier comparison with original code.
No need for parent in this branch
Methods, not functions
README cleanup