Getting working folder and install prefix from option

Hey @nschum, what I have done in this pull request was merging your awesome config feature with recent C++11 changes. Everything should be the same as the main repo except the last commit, in which working folders and install prefix are preserved in oclint::option. I hope it's easier for you to get relative `etc` path to the `oclint` binary. Again, appreciate your effort in this, let's work together to have it merged.