reduce dependency of ICU, undefine OffscreenTexture unless CgFX
moved vpvl2::extensions::gl to vpvl2::gl (except SimpleShadowMap)
added String::Converter#converterFromCodec
added vpvl2::extensions::qt:(Encoding|String) class
fixed crash caused by buffer overflow
migrated building system to QBS instead of qmake
should pass string length
make deployable, remove VPVM under qml due to deploy issue (debug only)