Introduce jquery formvalidator for com_newsfeed

[dgrammatiko]

Executive summary

This PR converts the form validation on com_newsfeed to use plain jquery (no mootools call on every form).
Also NO MORE INLINE SCRIPTS!

Testing

1. Apply first PR Reduce unneeded calls for mootools #4888 (!important)
2. Apply this PR
3. In the admin area go to com_newsfeed 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.

[smanzi]

@test success

[anibalsanchez]

@test success

[roland-d]

Moving to RTC as we have 2 successful tests.

This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/5050.

[dgrammatiko]

@roland-d All these PRs depend on #4888 so this one has to be RTC as well!

[roland-d]

@DGT41 Thanks for the heads-up, I read that and I am going through your PRs at this moment. So #4888 should be hit at some point as well :)

[smanzi]

@test success for this PR
Tested the set of: #5046 #5048 #5049 #5050 #5051 #5052 #5053 #5054 #5056 #5058 #5113 #5255