don't crash there yet when OpenGL version parsing fails

closes #5595
remove redundant OpenGL version check to avoid NREs
what if there is no vendor info to remove from version string
Fixed selectedAuthor in ModBrowserLogic not being the correct value if mod.Author is null
Remove redundant constructors
Compact lambda expressions in some (not all) places
Remove some stray semicolons
Use Any() instead of Count() == 0
Now that we're on .NET 4 again, reintroduce optional parameter for RegisterNewSquad
Remove unused usings
Use var everywhere