Upgrade solc to 0.5.x

[mrice32]

Upgrade to Solidity version 0.5.0. There are a few caveats with this change.

• We're using a release candidate of open zeppelin because they haven't done a stable release of 0.5.0 compatible contracts. We'll move to the real release once that's out.
• The maintainer of the solidity-coverage tool doesn't seem to be doing much work on it anymore. It works well, but the solidity parser it uses (forked and maintained by the same maintainer) hasn't been updated to work with 0.5.0. There's a PR out to update the parser, but it hasn't been reviewed or merged. Until that happens, we'll be manually replacing the package with the code from that PR (Added support for payable address sc-forks/solidity-parser#18 (comment)).

This compiler/language update contains a lot of breaking changes, so I also upgraded any packages that might depend on the output of the compiler in some way.