Add a possibility to redownload another Flash Projector version later

[GerRudi]

Add a possibility to re-download another Flash Projector version later in the settings.

[vScherb]

And an ability to select when starting with an default option.
Otherwise the client has to be restarted every time the user wants to change the flash projector.

[GerRudi]

Changing flash projector versions isn't like changing clothes. This usually only has to be done once or twice (if at all) to compare the performance.

[GerRudi]

requires a more modular version of the implementation of the initial setup - currently low priority