Make new type system default

[jitsedesmet]

The new type system has been put behind a flag in #117. We should try to make this new type system the default. This means that we should optimize the new system some more. Even seemingly small optimization mean a lot here. The functions that require special attention are:

• experimentalTransformLiteral in lib/transformers/TermTransformer
• isSubTypeOf in lib/util/TypeHandling
• getSubTreeWithArg in lib/functions/OverloadTree

Of course we could also look at the few functions that are called within these functions.

I don't have any suggestions on how to start optimizing these functions. If there are any more questions regarding this issue you should be able to contact me on them.

[jitsedesmet]

If I'm not mistaken, the optimization of getSubTreeWithArg shouldn't matter so much if we use the cache.