D: Add remaining keywords, rdmd in execute command

I added the remaining keywords that weren't present before. See this:
http://dlang.org/lex.html

Additionally, I also added rdmd in execute which enables the developer to execute D program on fly.
> maybe they should be highlighted as secondary instead?

Personally I think secondary keywords should be for type keywords, e.g. `int`. But we don't do that for e.g. C highlighting yet, so that's a separate discussion really.