Due to poor and imprecise implementation, revert "Replace usage of boost's lexical_cast with std's stringstreams. Performance-wise these probably are not as efficient, but doesn't really matter as the ToString and ParseString functions are used very little, if at all in the codebase. #595"

This reverts commit 71bfc50df74a7aaf404f6e2e9b06a6efd5cb2568.
Replace usage of boost::thread with Qt equivalents in Profiler.