Add language toolbar button

Also adds flag icon for each language.

One limitation is that the language button doesn’t work properly when
accessed via the “more” menu of the page controls.

@BramChen - could you help me choose the most appropriate flags to use
for the variants of Chinese?

languages/de-AT/Flag.tid

@@ -0,0 +1,8 @@
+title: $:/language/Flag
+type: image/svg+xml
+
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="900" height="600">
+<rect fill="#ed2939" width="900" height="600"/>
+<rect fill="#fff" y="200" width="900" height="200"/>
+</svg>

languages/de-DE/Flag.tid

@@ -0,0 +1,12 @@
+title: $:/language/Flag
+type: image/svg+xml
+
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+	"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg xmlns="http://www.w3.org/2000/svg" width="1000" height="600" viewBox="0 0 5 3">
+	<desc>Flag of Germany</desc>
+	<rect id="black_stripe" width="5" height="3" y="0" x="0" fill="#000"/>
+	<rect id="red_stripe" width="5" height="2" y="1" x="0" fill="#D00"/>
+	<rect id="gold_stripe" width="5" height="1" y="2" x="0" fill="#FFCE00"/>
+</svg>

languages/fr-FR/Flag.tid

@@ -0,0 +1,5 @@
+title: $:/language/Flag
+type: image/svg+xml
+
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="900" height="600"><rect width="900" height="600" fill="#ED2939"/><rect width="600" height="600" fill="#fff"/><rect width="300" height="600" fill="#002395"/></svg>

languages/it-IT/Flag.tid

@@ -0,0 +1,32 @@
+title: $:/language/Flag
+type: image/svg+xml
+
+<?xml version="1.0" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<svg 
+	height="1000" 
+	width="1500" 
+	version="1.1" 
+	viewBox="0 0 3 2" 
+	xmlns="http://www.w3.org/2000/svg" 
+	xmlns:xlink="http://www.w3.org/1999/xlink">
+	<desc>Bandiera della Repubblica Italiana PMS 20060414</desc>
+<!--
+	from http://commons.wikimedia.org/wiki/Image:Bandiera_della_Repubblica_Italiana_PMS_20060414.svg
+	this text is in the public domain
+-->
+	<rect 
+		fill="#009246" 
+		height="2" 
+		width="1" />
+	<rect 
+		fill="#f1f2f1" 
+		height="2" 
+		width="1" 
+		x="1" />
+	<rect 
+		fill="#ce2b37" 
+		height="2" 
+		width="1" 
+		x="2" />
+</svg>

languages/ja-JP/Flag.tid

@@ -0,0 +1,8 @@
+title: $:/language/Flag
+type: image/svg+xml
+
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="900" height="600">
+<rect fill="#fff" height="600" width="900"/>
+<circle fill="#bc002d" cx="450" cy="300" r="180"/>
+</svg>