Support overriding solc options

[macalinao]

http://truffleframework.com/docs/advanced/configuration#solc

This documentation is incorrect. The only thing configurable is the optimizer.

[cgewecke]

@macalinao @vecheslav Hi.

We're doing quite a bit of work on truffle-compile for the next release. Which options would you like to configure? The current option set is specified here in the truffle code. Some of these are necessary because they are enumerated in the contract-schema we've committed to. Would like to hear your use-cases though and get some understanding of how this could be better.