Fix wrong results returned by isEnabled

When language filter plugin is disabled and language filter is enabled in code using JFactory::getApplication()->setLanguageFilter(true) calling JLanguageAssociations->isEnabled causes notices and fatal errors and returns wrong result if item associations are in fact disabled.

What happens is that JPluginHelper::getPlugin returns empty array when certain plugin is disabled and since there is no params to be passed to JRegistry and $enabled gets default value.
Correct enQueueMessage to enqueueMessage
[bug] [33688] JApplicationCms::getRouter is a static method.
Closes #3548
[bug] [33662] Microdata in single article view causes invalid HTML
Close #3511, close #3555
Merge pull request #3562 from sovainfo/patch-5

Correct enQueueMessage to enqueueMessage
[bug] Fix the unit tests, close #3550
[bug] [32258] FOFModel::getTmpInstance() clears input before getItemList() is run
Close #2227
Correcting error in sr-YU
[bug] [32295] Add gradient for background at the login screen for IE10
Close #2321
Generated CSS from LESS using build/generatecss.php
[imp] [33641] Add time unit in cache settings description
Close #3499
[bug] [33701] User Notes Categories - Error in menu and filter selection
Close #3559
Fixed missing space in toolbar buttons (type modal)
Merge pull request #3572 from nonumber/patch-1

Fixed missing space in toolbar buttons (type modal)
[bug] [33413] Cannot upload file to sub-folder in Media Manager in back end
Close #3575
[bug] [32957] Removing doubled description tab in template styles
Close #3049
[bug] [33625] Replace "bootstrap_size":"1" with "bootstrap_size":"0"
Close #3470
[bug] [33600] Remove validate-jquery-uncompressed.js
Close #3426
[imp] [32323] Removes excessive padding-top on the body element when the viewport is at 738px wide
Close #2650
[#32862] Removed // comments from bootstrap css.

The // comments are not intended to be present in the css files.  They are
only present in the .less files to identify changes from standard bootstrap.