Optimized the compilation, and added a new option to alloy's compile command

In large projects, the compile command may take a while. This commit adds the support for a "file" alloy compile option, which restricts the operations on the compilation of this specific file. This might be particularly suited for use with grunt and TiShadow, to speedup large projects processing.
tabs vs spaces
Merge pull request #625 from xavierlacot/feature/speedup-compile

[ALOY-620] another way of speeding up alloy compilation