Remove plugin manager and observer classes

We don't really need the observer pattern, so let's simplify the code.

Signed-off-by: Michal Čihař <michal@cihar.com>
bug-4473: incorrect result count when having clause is used w/o group by

Signed-off-by: Chirayu Chiripal <chirayu.chiripal@gmail.com>
Translated using Weblate (French)

Currently translated at 100.0% (2834 of 2834)
Fixed cookie based login for installations without mcrypt

bug #4469

Signed-off-by: Michal Čihař <michal@cihar.com>
Translated using Weblate (Interlingua)

Currently translated at 54.5% (1512 of 2770)
Merge remote-tracking branch 'origin/QA_4_2' into QA_4_2
Fix comments

Signed-off-by: Michal Čihař <michal@cihar.com>
Merge remote-tracking branch 'origin/QA_4_2'
Translated using Weblate (Interlingua)

Currently translated at 55.1% (1563 of 2834)
Merge remote-tracking branch 'origin/master'
Merge pull request #1252 from nijel/remove-observer

Remove plugin manager and observer classes
PMA console, history and bookmarks.

Modified: resizer of navigation bar: whole-time-bind events removed.

Signed-off-by: Edward Cheng <c4150221@gmail.com>
Merge pull request #1251 from WhaleWatching/console

PMA console, history and bookmarks.
Fix merge conflict

Signed-off-by: Marc Delisle <marc@infomarc.info>
Fix merge conflict

Signed-off-by: Marc Delisle <marc@infomarc.info>