Minimal dependencies for Solidity on Ubuntu 16.04, removed those for older Ubuntu versions for now (they were a bit confusing).
Removed --all and added -DETHASHCL=0 to ethbuild.sh when building Solidity only.
The brew install boost --c++11 command failed for me due to an outdated version of Node.js.
`brew upgrade` fixed this. I think it should be in the documentation to reduce the number of errors on install
Add explanation to the documentation that the package name changes from `libjson-rpc-cpp-dev` to `libjsonrpccpp-dev` and is supplied by the universe repository instead of the Ethereum PPA.