This commit introduces ErrorReporter, a utility class which consolidates
all of the error logging functionality into a common set of functions.
It also replaces all direct interactions with an ErrorList with calls to
an ErrorReporter.
This commit resolves issue #2209
Otherwise, I see a build failure:
test/libjulia/Parser.cpp:92:6: error: ‘bool dev::solidity::test::{anonymous}::successAssemble(const string&, bool)’ defined but not used [-Werror=unused-function]
bool successAssemble(string const& _source, bool _allowWarnings = true)
^~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
