move the _solidity binding to the JSON compiler input output format

[konradkonrad]

Problem description

The _solidity module currently does a lot of input/output parsing "by hand". This is prone to break on changes of solc and does not easily allow to use all new features (e.g. #737 #376).

Proposed solution

Instead of replicating the features of the solc command line client, it should be considered to move to the "Compiler Input and Output JSON Description" and just pass through those options.

[axic]

Please do this move :)