Build system improvement

[ntavish]

It would be nice to have per file interpreter according to file extension, like python for '.py', bash for '.sh'. Apart from that, the per project 'Build system', should be the command that is to be executed inside the project directory. For example 'make', this would make adding build support for C/C++ makefile based projects easy(also other languages).

[ntavish]

For the file extension based interpreter thing, we can just mark files executable, and it will automatically execute with the correct interpreter using the shebang, like #!/usr/bin/python or #!/bin/bash. Other than that, the build system/execution is ok. Thanks!