Add buttons to ARE control pane to start WebACS/Webpage

[klues]

It should possible to start:

• the ARE webserver landing page (see https://github.com/asterics/AsTeRICS/issues/210)
• the currently deployed model in WebACS

directly with a button in the ARE control pane or with a shortcut.

[klues]

now looks like this: http://prntscr.com/hmwgcn

[klues]

done with https://github.com/asterics/AsTeRICS/pull/214