Convert the conversation list into a real fragment.

It was a fragment before, but it's functionality was inappropriately
split between the various layers.

This also sets us up better to do tablet stuff in the future, if we
choose to do that.

AndroidManifest.xml

@@ -122,11 +122,11 @@
     <activity android:name=".InviteActivity"
               android:theme="@style/TextSecure.HighlightTheme"
               android:windowSoftInputMode="stateHidden"
-              android:parentActivityName=".ConversationListActivity"
+              android:parentActivityName=".MainActivity"
               android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize">
         <meta-data
             android:name="android.support.PARENT_ACTIVITY"
-            android:value="org.thoughtcrime.securesms.ConversationListActivity" />
+            android:value="org.thoughtcrime.securesms.MainActivity" />
     </activity>
 
     <activity android:name=".PromptMmsActivity"
@@ -189,16 +189,8 @@
         </intent-filter>
     </activity>
 
-
-    <activity android:name=".ConversationListActivity"
-              android:label="@string/app_name"
-              android:launchMode="singleTask"
-              android:theme="@style/TextSecure.LightNoActionBar"
-              android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize"
-              android:exported="true" />
-
     <activity-alias android:name=".RoutingActivity"
-                    android:targetActivity=".ConversationListActivity"
+                    android:targetActivity=".MainActivity"
                     android:exported="true">
 
         <intent-filter>
@@ -214,24 +206,14 @@
 
     </activity-alias>
 
-    <activity android:name=".ConversationListArchiveActivity"
-              android:label="@string/AndroidManifest_archived_conversations"
-              android:launchMode="singleTask"
-              android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize"
-              android:parentActivityName=".ConversationListActivity">
-        <meta-data
-                android:name="android.support.PARENT_ACTIVITY"
-                android:value="org.thoughtcrime.securesms.ConversationListActivity" />
-    </activity>
-
     <activity android:name=".conversation.ConversationActivity"
               android:windowSoftInputMode="stateUnchanged"
               android:launchMode="singleTask"
               android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize"
-              android:parentActivityName=".ConversationListActivity">
+              android:parentActivityName=".MainActivity">
         <meta-data
                 android:name="android.support.PARENT_ACTIVITY"
-                android:value="org.thoughtcrime.securesms.ConversationListActivity" />
+                android:value="org.thoughtcrime.securesms.MainActivity" />
     </activity>
 
     <activity android:name=".longmessage.LongMessageActivity" />
@@ -468,6 +450,10 @@
         android:theme="@style/TextSecure.LightNoActionBar"
         android:windowSoftInputMode="adjustResize"/>
 
+    <activity android:name=".MainActivity"
+              android:theme="@style/TextSecure.LightNoActionBar"
+              android:configChanges="touchscreen|keyboard|keyboardHidden|orientation|screenLayout|screenSize" />
+
     <service android:enabled="true" android:name="org.thoughtcrime.securesms.service.WebRtcCallService"/>
     <service android:enabled="true" android:name=".service.ApplicationMigrationService"/>
     <service android:enabled="true" android:exported="false" android:name=".service.KeyCachingService"/>