Port Signal's emoji implementation to Briar

Add functionality to save and restore recently used Emojis

Update emoji and add new categories based on AOSP's XML file

briar-android/artwork/ic_emoji_emoticons.svg

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   id="svg2"
+   version="1.1"
+   inkscape:version="0.91 r13725"
+   width="24"
+   height="24"
+   viewBox="0 0 24 24"
+   sodipodi:docname="ic_emoji_emoticons.svg">
+  <metadata
+     id="metadata8">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title></dc:title>
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <defs
+     id="defs6" />
+  <sodipodi:namedview
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1"
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     inkscape:pageopacity="0"
+     inkscape:pageshadow="2"
+     inkscape:window-width="1920"
+     inkscape:window-height="1021"
+     id="namedview4"
+     showgrid="false"
+     inkscape:zoom="4.6354778"
+     inkscape:cx="47.926788"
+     inkscape:cy="24.127496"
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+     inkscape:window-y="23"
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+     inkscape:current-layer="svg2" />
+  <path
+     style="fill:#000000;fill-opacity:1"
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+</svg>