Create implicit executable

[sorki]

which will use hint (similar to implicitpipe or implicit-servant) to process its Haskell code file argument.

Related to #318

[julialongtin]

looks like the idea that became implicit-interpreter? :)

[sorki]

Not quite, but the interpreter is a stepping stone for this and #318.

I think it can be added as executable in the interpreter package and will try it. Ideally it would be part of implicit but that would require bit more splitting (interpreter library currently doesn't depend on implicit but the testsuite does).