Add experimental MPV player backend (#161)

Experimental MPV player backend

Related to #14, #22, & #85

You can switch to MPV in advanced settings and toggle using hardware
decoding or not.

This uses code and buildscripts from
https://github.com/mpv-android/mpv-android, plus other third party
libraries to build MPV

app/config/libraries/lib_dav1d.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.videolan.dav1d",
+  "developers": [],
+  "artifactVersion": "master",
+  "description": "dav1d is an AV1 cross-platform decoder, open-source, and focused on speed and correctness",
+  "name": "dav1d",
+  "licenses": [
+    "dav1d"
+  ],
+  "website": "https://github.com/videolan/dav1d"
+}

app/config/libraries/lib_fribidi.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.fribidi.fribidi",
+  "developers": [],
+  "artifactVersion": "1.0.16",
+  "description": "The Free Implementation of the Unicode Bidirectional Algorithm",
+  "name": "fribidi",
+  "licenses": [
+    "lgpl-2.1"
+  ],
+  "website": "https://github.com/fribidi/fribidi"
+}

app/config/libraries/lib_libass.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.libass.libass",
+  "developers": [],
+  "artifactVersion": "master",
+  "description": "libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format",
+  "name": "libass",
+  "licenses": [
+    "libass"
+  ],
+  "website": "https://github.com/libass/libass"
+}

app/config/libraries/lib_libplacebo.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.haasn.libplacebo",
+  "developers": [],
+  "artifactVersion": "master",
+  "description": "libplacebo is, in a nutshell, the core rendering algorithms and ideas of mpv rewritten as an independent library",
+  "name": "libplacebo",
+  "licenses": [
+    "lgpl-2.1"
+  ],
+  "website": "https://github.com/haasn/libplacebo"
+}

app/config/libraries/lib_libunibreak.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.adah1972.libunibreak",
+  "developers": [],
+  "artifactVersion": "6.1",
+  "description": "an implementation of the line breaking and word/grapheme breaking algorithms as described in Unicode Standard Annex 14 (UAX #14) and Unicode Standard Annex 29 (UAX #29)",
+  "name": "libunibreak",
+  "licenses": [
+    "libunibreak"
+  ],
+  "website": "https://github.com/adah1972/libunibreak"
+}

app/config/libraries/lib_mbedtls.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.Mbed-TLS.mbedtls",
+  "developers": [],
+  "artifactVersion": "v3.6.4",
+  "description": "Mbed TLS is a C library that implements X.509 certificate manipulation and the TLS and DTLS protocols",
+  "name": "mbedtls",
+  "licenses": [
+    "gpl-2.0"
+  ],
+  "website": "https://github.com/Mbed-TLS/mbedtls"
+}

app/config/libraries/lib_mpv.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.mpv-player.mpv",
+  "developers": [],
+  "artifactVersion": "master",
+  "description": "mpv is a free (as in freedom) media player for the command line",
+  "name": "mpv",
+  "licenses": [
+    "gpl-2.0"
+  ],
+  "website": "https://github.com/mpv-player/mpv"
+}

app/config/libraries/lib_mpv_android.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "com.github.mpv-android.mpv-android",
+  "developers": [],
+  "artifactVersion": "master",
+  "description": "mpv-android is a video player for Android based on libmpv",
+  "name": "mpv for Android",
+  "licenses": [
+    "mpv-android"
+  ],
+  "website": "https://github.com/mpv-android/mpv-android"
+}

app/config/libraries/lin_freetype.json

@@ -0,0 +1,11 @@
+{
+  "uniqueId": "org.freetype",
+  "developers": [],
+  "artifactVersion": "2.14.1",
+  "description": "FreeType is a freely available software library to render fonts",
+  "name": "freetype",
+  "licenses": [
+    "gpl-2.0"
+  ],
+  "website": "https://freetype.org"
+}