Fix the send button's touch highlight color

Introduce a generic touch highlight background drawable, and use the
proper shades of blue (and gray on v19+).

res/drawable/send_button_background.xml

@@ -1,24 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<selector xmlns:android="http://schemas.android.com/apk/res/android">
-    <!-- pressed -->
-    <item android:state_pressed="true" >
-        <shape>
-            <solid android:color="#FF33B5E5" />
-        </shape>
-    </item>
-
-    <!-- focused -->
-    <item android:state_focused="true" >
-        <shape>
-            <solid android:color="#FF33B5E5" />
-        </shape>
-    </item>
-
-    <!-- default -->
-    <item>
-        <shape>
-            <solid android:color="#00ffffff" />
-        </shape>
-    </item>
-
-</selector>

res/drawable/touch_highlight_background.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:state_pressed="true" android:drawable="@color/touch_highlight" />
+    <item android:drawable="@android:color/transparent" />
+</selector>

res/layout/conversation_activity.xml

@@ -108,7 +108,7 @@
                     android:layout_width="wrap_content"
                     android:layout_height="fill_parent"
                     android:layout_gravity="center_vertical"
-                    android:background="@drawable/send_button_background"
+                    android:background="@drawable/touch_highlight_background"
                     android:contentDescription="@string/conversation_activity__send"
                     android:nextFocusLeft="@+id/embedded_text_editor"
                     android:padding="12dp"

res/values-v19/colors.xml

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
+    <color name="touch_highlight">#10000000</color>
     <color name="card_background_active">#99bebebe</color>
 </resources>

res/values/colors.xml

@@ -11,6 +11,7 @@
 
     <color name="textsecure_holo_blue_light">#ff33b5e5</color>
 
+    <color name="touch_highlight">#400099cc</color>
     <color name="card_background_active">#9933b5e5</color>
 
     <color name="conversation_item_sent_background_dark">#ff284e0a</color>