Improvements to layout, syntax highlighting, and display of the source code

Please consider some modification to the ScalaFX Ensemble:
* Corrected layout so frame/stage can be re-sized and look properly on screens with different size
* Dependencies, including ScalaFX, updated to latest versions
* Removed duplicate version of examples source code, actual example code used in Ensemble code is displayed to the user
* Added syntax highlighting to the displayed source code
* The displayed source code is turned into a JFXApp so it can be cut and pasted for stand alone execution. Note explanation to commit [9aa11bc](https://github.com/jpsacha/scalafx-ensemble/commit/9aa11bccdfe14483b6cf47ce5324c45ead672426)

I couple of things I am planing next:
* A button to copy source to clipboard (to avoid additional line breaks if copied directly from the viewer)
* A button to save sample as an SBT project
* See if the sample code presented to the user can be (semi)automatically tested, possibly using the option to save it as an SBT project
* Review examples and simplify the code to best demonstrate ScalaFX capabilities