Changed Windows opengl to 3.0
Fixed windows specific warning. Minor optimization to #include directives.
Improved appearance on Windows explorer and taskbar.
changed object to use std::abs
Add list of commits to be checked and merged to TODO.txt

The listed commits are on the 'experiment' branch that was used to test how
multiple threads could work. At the moment the multithread changes are not
used, but there are some miscellaneous commits that could be merged. Some of
the changes are already cherry-picked to master.