port to Qt5 and QtMultimedia
fix README
fix the missing newline at the end of README.me
media preview ui enhancement
fix media preview timing
add the missing suffix to the video element's volume property and rename
fix a bug of non-starting videos
use a type alias for readability
add a missing scaling mode to video elements
process application events before pausing a video element (it prevent it to flicker)
add a black background behind video elements
using the new signal/slot syntax
using QStringLiteral for read-only strings
commit missing changes of 8a57c052b57e5fccd82dcc477af897efd1b1557b
fix invalid loadPlugin() slot usage (bug introduced in 55c43b6c49dc9068de811ee25ae48ccde0828154)
Merge branch 'qt5'

Conflicts:
	core/imageelement.cpp
	core/mainwindow.cpp