Do not change browser title on autorefresh

fixes #6168
Move hover menu downward

fixes #6169
Upgrade JShrink to 1.0

refs #6165
Upgrade htmlpurifier to 4.6.0

refs #6165
Upgrade lessphp

* Upgrade from 0.3.9 to 0.4.0
* Document package source
* Remove overhead

refs #6165
refs #6166
Put focus into search field on initial page load

fixes #6170
Detect and handle remote links

Currently they trigger XHR requests if not given a special target.

fixes #6159
Completely ignore remote links

There are no issues with "returning true" so this should be the
preferred way. No need to fall back on "window.open" here.

fixes #6159
Initial "click" handling for dropdown tabs

Still uncomplete, there are a number of edge cases that need to be
handled. Keyboard navigation is one of them, hover/click distinction
is another one.

refs #6167
Improve console log message on errors like 404

Former '404 Not found' plus weird HTML snippet is now: '404 Not Found:
 Page not found. Enabling the "bpapp" module might help!'
Restore click behaviour for table links and rows

Multiselect handlers should influence only multiselect tables. Still
unhappy with current behaviour, but links should work fine right now.

refs #6162
Upgrade Parsedown to 1.0.0-rc.4

Please note that this invalidates my img size patch, I forgot to bring
it upstream. Still TBD.

refs #6165
Monitoring_ListController: autorefresh matrix...

...and notification views

fixes #6152
CSS: Highlight a couple of elements on focus

Menu, tabs, hover menu and dropdown tabs. Keyboard navigation starts
making sense right now.

refs #6164
Merge remote-tracking branch 'origin/master' into feature/query-interfaces-6018
Vagrant: Add Icinga2 and test configuration

refs #6127
Vagrant/Icinga2: Optimize test configuration
Vagrant/Icinga2: Upgrade to snapshots and optimize configuration

refs #6127
Vagrant/Icinga2: Add dependencies for test config

refs #6127
Merge branch 'feature/vagrant-icinga2-core-6127'

Switch core for Icinga Web to Icinga2 package install and add test configuration.

Consider: Run 'vagrant priovion' and remove /etc/icingaweb configuration folder
to install new core and let new icingaweb configuration take place.

resolves #6127