WIP: add experimental clickable links with dialog

(copy / open). Bug remaining for selectable text

@@ -30,6 +30,11 @@
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
+            <intent-filter>

@@ -230,0 +241,4 @@
+                                },
+                                activeTrackColor: settings.theme.defaultButtonActiveColor(),
+                                inactiveTrackColor: settings.theme.defaultButtonDisabledColor(),
+                                secondary: Icon(Icons.link, color: settings.current().mainTextColor()),

@@ -58,0 +68,4 @@
+        text: widget.content + '\u202F',
+        // TODO: onOpen breaks the "selectable" functionality. Maybe something to do with gesture handler?
+        options: LinkifyOptions(humanize: false),
+        linkifiers: [UrlLinkifier()],  // TODO: double-check on this (only web links to avoid Android messiness)

@@ -58,0 +66,4 @@
+    } else {
+      wdgMessage = SelectableLinkify(
+        text: widget.content + '\u202F',
+        // TODO: onOpen breaks the "selectable" functionality. Maybe something to do with gesture handler?

@@ -93,0 +123,4 @@
+        builder: (BuildContext bcontext) {
+          return Container(
+              // TODO: Ask re: hard-coded height
+              height: 200, // bespoke value courtesy of the [TextField] docs

@@ -93,0 +135,4 @@
+                          "Opening this link will launch an application outside of Cwtch and may reveal metadata or otherwise compromise the security of Cwtch. Only open links from people you trust. Are you sure you want to continue?"
+                        ),
+                        // TODO: Ask about styling preferences (should this be a reusable "inline-button"?)
+                        Flex(direction: Axis.horizontal, mainAxisAlignment: MainAxisAlignment.center, children: <Widget>[

@@ -93,0 +144,4 @@
+                                Clipboard.setData(new ClipboardData(text: link.url));
+
+                                // TODO: Ask about desired SnackBar + modal behaviour
+                                final snackBar = SnackBar(

@@ -228,2 +228,4 @@
                                 secondary: Icon(Icons.attach_file, color: settings.current().mainTextColor()),
                               ),
+                              SwitchListTile(
+                                title: Text("Enable Clickable Links", style: TextStyle(color: settings.current().mainTextColor())),