Give llambda a proper Scala package

- Rename llambda package to io.llambda.compiler. The "llambda.io" is
  owned by myself and the "compiler" allows room in the namespace for
  other Scala/Java projects related to the language.

- Move all the files from src/main/scala/llambda to src/main/scala. The
  single "llambda" directory src/main was basically a trick to make Vim
  populate new Scala files with our old package name
Move llvmir to its own subproject

The type generator rewrite might depend on llvmir. However, it's a bit
clunky to depend on the entire compiler to access it. Move it to its own
subproject in the package io.llambda.llvmir and have the compiler depend
on it.