Ui enhancements

I've splitted the UI enhancements and the switch spring-boot 1.2.

The UI has several new features:

* Easier (more visual) logger-level management
* Enhanced details view:
 * Cleaner Memory details
 * Garbage collection details
 * Classpath details
 * Support for richGauge metrics (needs spring-boot 1.2.x on client)
 * Datasource usage (needs spring-boot 1.2.x on client)
 * Detailed health checks info (needs spring-boot 1.2.x on client)
* JMX-view for interacting with MBeans (using jolokia)
* Threads-view to dump all Threads and view the dump
* Button to remove offline Applications

Under the hood:
* css cleanup
* some changes needed for minification

Some screenshots:
![screenshot-details](https://cloud.githubusercontent.com/assets/8779225/4981280/8873f2f6-6907-11e4-893c-9f2139973986.png)
![screenshot-jmx](https://cloud.githubusercontent.com/assets/8779225/4981281/88962df8-6907-11e4-8443-e9b3e56be871.png)
![screenshot-logging](https://cloud.githubusercontent.com/assets/8779225/4981282/88b36832-6907-11e4-940b-4ba9b8d6e8e3.png)