Introduce jquery formvalidator for com_languages

#### Executive summary

This PR converts the form validation on com_languages to use plain jquery (no mootools call on every form).
Also NO MORE INLINE SCRIPTS!

#### Testing

1. Apply first PR #4888 (!important)
2. Apply this PR
3. In the admin area go to com_languages and try to submit any form.

If no javascript errors are logged in your browser and the functionality remains the same your test is a pass in any other case please report the errors here

Please also check these:
administrator/index.php?option=com_checkin should demonstrate multiselect without mt
administrator/index.php?option=com_users&view=mail should demonstrate form sent and validate without mt
administrator/index.php?option=com_modules should demonstrate multiselect and combobox without mt
http://localhost/administrator/index.php?option=com_admin&view=sysinfo should demonstrate highlighter.js without mt
Logout and log in to demonstrate the use of noframes without mt.
@Fedik This is indeed, as i said before, unneeded. The reason that I put it there was just to unify the script code. So when devs tries to bring their code to 3.4 (or whenever) they see a unique pattern on the core and just follow it.
What is very interesting for admin area is that if you take a 3.3.6 and apply all those PRs, for all pages (except the edit ones where you have a modal) the page loading time decreases by 20-30%. :tada: 
Just to be clear here: if people think that this is a bad practice, I can revert this code to be plain js, no prob! :grey_question: