[fix][32285] Support JSON response in Internet Explorer < 10. Fixes #3653

Internet Explorer older than 10 does not accept
Content-Type: application/json
and would start to download response.

Also header Content-Disposition
would force IE to download response.

It would only occur if you would try to upload file by ajax in IE < 10,
because IE 7 - 9 do not support uploading file with XHR.

To test it see a test module in Code Tracker:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_id=8103&tracker_item_id=32285

Related PR which are already outdated and closed:
https://github.com/joomla/joomla-cms/pull/2013
https://github.com/joomla/joomla-cms/pull/2166

Update json.php

Removed trailing whitespace

Update json.php

By default set mime type application/json and change it to text/plain only in a specific situation
[fix][32750] IE 10 - Isis -> Image can't be inserted via Image Button. Fixes #3932

http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=32750&start=0

1. Use Internet Explorer 10
2. edit or write an article
3. Click on Image button below
4. choose an image and click on insert.
5. Nothing happens.
6. apply patch
7. clean cache
8. redo 1-4 and make sure it work now.
[imp][32131] Refactored method to use server variables. Fixes #3886

Setting test database collation
[fix][33923] PHP Notice: Undefined index: HTTP_USER_AGENT in (sysinfo.php + debug.php). Fixes #3859

PHP Notice: Undefined index: HTTP_USER_AGENT in (sysinfo.php + debug.php)

PHP Notice: Undefined index: HTTP_USER_AGENT in (sysinfo.php + debug.php)
[imp][33585] JTable improvement to the bind method. Fixes #3423

Amend doc block for the contact.php var

Also perform same application to newsfeeds

oops :P

Add unit test for functionality

Use json_encode instead of JRegistry

Use native PHP function for increased performance
error in da-DK string
Revert "[imp][32131] Refactored method to use server variables. Fixes #3886"

This reverts commit 67f506a66f6bf47a121996c0249cae307f203ed7.

Jenkins failed with:
````
JDatabaseDriverMysqliTest::testGetCollation
Line:130 The getCollation method should return the collation of the database.
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'utf8_general_ci'
+'latin1_swedish_ci'

/var/lib/jenkins/jobs/cms/workspace/tests/unit/suites/database/driver/mysqli/JDatabaseDriverMysqliTest.php:131
````
and
````
JDatabaseDriverMysqlTest::testGetCollation
Line:130 The getCollation method should return the collation of the database.
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'utf8_general_ci'
+'latin1_swedish_ci'

/var/lib/jenkins/jobs/cms/workspace/tests/unit/suites/database/driver/mysql/JDatabaseDriverMysqlTest.php:131
````