Allow filters to be build as unicode
Added local baseclasses for DirectShow filters

- DSHOW_BASE environmental variable is not needed anymore
Moved dshowhelper, DXUtil, fontEngine and Win7RefreshRateHelper under dshow folder
Moved MPC-HC subtitle engine under DirectShowFilters
Changed BDReader to use libbluray as GIT submodule
Updated build scripts to match the structural changes that have been done to native components