Terasology Lite version selection is empty

[jdrueckert]

When I select "Terasology Lite (engine-only)" instead of the default "Terasology", the version selection drop down below is empty and does not have any values to select.
This was observed in a self-built launcher on master branch, commit 86045408ca574d339973a59519a0e05b2e0c88f5.

How to reproduce

1. Start the launcher
2. In the upper selection drop-down, select "Terasology Lite (engine-only)"
3. Observe that the current selection of the lower selection drop-down is empty
4. Observe that there are no entries for the lower selection drop-down

[skaldarnar]

This is most likely a left-over issue from reducing the surface of available games and slimming down the game selection process in the launcher.

We currently only look for Omega builds from Github, and, if enabled, for nightly builds of Omega directly from Jenkins.

I propose to just remove the option from the launcher, and further simplify the selection. Probably in combination with #634 and other UI-related topics.

[skaldarnar]

Completed by #684.