Optimize cache enabled recompile

[mattsse]

Is your feature request related to a problem? Please describe.
with caching enabled only dirty files are provided to solc. in #998 this was changed so that the CompilerInput also included all the file's imports, so that solc does not need to resolve all required files itself. However this results in solc compiling all those clean files with the shared output settings, which is unnecessary as for clean files we don't require bytecode etc.

Describe the solution you'd like

Take #998 approach and modify the settings dynamically, to tell solc not to include bytecode etc in the output for clean files.