Add new file source element for Universal Windows Platform

Due to the strict access permission rule of UWP, only app's local
storage directory can be accessed by traditional Win32 APIs.
To read file located in arbitrary path, an app should use StorageFile
object returned by Windows::Storage::Pickers::FileOpenPicker interface.

This new element supports both uri based file open like filesrc element
and StorageFile based file open for UWP app. To make it work with StorageFile
interface, an application should pass the pointer to StorageFile interface
by "storage-file" property.
25 jobs for winrt-plugin in 25 minutes and 36 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Preparation
passed #1462465
gst indent

00:00:30

passed #1462464
manifest

00:00:33

 
  Build
passed #1462475
gstreamer
build cerbero cross-android universal

00:07:43

passed #1462479
gst-ios-13.2
build cerbero cross-ios universal

00:16:55

passed #1462476
gstreamer
build cerbero cross win32

00:05:25

passed #1462477
gstreamer
build cerbero cross win64

00:03:26

passed #1462474
gstreamer
build cerbero fedora x86_64

00:04:38

passed #1462478
gst-macos-10.15
build cerbero macos x86_64

00:11:53

passed #1462470
build clang fedora x86_64

00:06:35

passed #1462466
build fedora x86_64

00:06:48

passed #1462473
docker windows 1809
build msys2

00:23:35

passed #1462467
build nodebug fedora x86_64

00:08:04

passed #1462468
build static fedora x86_64

00:12:14

passed #1462469
build static nodebug fedora x86_64

00:03:13

passed #1462471
docker windows 1809
build vs2017 amd64

00:10:52

passed #1462472
docker windows 1809
build vs2017 x86

00:10:38

 
  Test
passed #1462480
gstreamer
check fedora

00:03:40

passed #1462481
gstreamer
integration testsuites fedora 1/4

00:11:59

passed #1462482
gstreamer
integration testsuites fedora 2/4

00:12:45

passed #1462483
gstreamer
integration testsuites fedora 3/4

00:11:26

passed #1462484
gstreamer
integration testsuites fedora 4/4

00:18:11

passed #1462485
gstreamer
valgrind bad

00:05:19

 
  Integrate
passed #1462486
cross-android universal examples

00:08:32

passed #1462488
gst-ios-13.2
cross-ios universal examples

00:03:53

passed #1462487
documentation

00:05:15