Afdarts RTS: version 0.3.4 released

The main changes in Afdarts 0.3.4 are new campaign scenarios, an AI difficulty option which makes the AI easier by default, a subtly improved UI for selecting and moving units, and an improved scenario format. I disabled the optimization which caused crashes in versions 0.3.2 beta and 0.3.3 beta, but it is still enabled in the Visual Basic IDE. Slings are now cheaper, so hopefully they are worth the price. Afdarts still needs some work in missions 4 and 6, graphics, and sound before version 1, and will probably benefit from cutscenes.