Refactor compile.go and exclude some files during compilation

[minhnhatnoe]

Uploaded files recognized by Kjudge ("statements.pdf", "statements.md", "compare", ".stages") are excluded during compilation. Uploaded .sh files, however, are not excluded.

Also broke compile.go into multiple small files.

[minhnhatnoe]

Just realized there was a couple of logic errors, so nuking this branch.