Theme settings and Mobile theme

- Readd commit c4cd02da1b7ebdf442e04d900b312bfb5ca8ad31 by @nmpetkov (which got lost for some reason)
- loading Mobile_Detect.php via composer now
- added ability to select if the mobile them shall be applied for smartphones, tablets or both.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | --
| Fixed tickets | --
| Forum topics | http://community.zikula.org/module-Forum-viewtopic-topic-59491-start-0.htm
| License       | MIT
| Doc PR        | --