LLAP: refactor prototype code to salvage some parts

After looking at prototype in discussion, there were some changes, such as hiding I/O layer in the service itself rather than exposing it directly (inputformat is too inflexible as an interface and has some other limitations), abandoning intermediate format (it is too much work, takes up more space, and for it to make more sense vectorized code should directly process it, which won't happen for a long time), etc.
Refactor prototype, throw away code, move other code.