Add installation documentation.

Remove unused rosinstall file and rename the correct one to .rosinstall.

rosjava.rosinstall → .rosinstall

 - hg:
-    local-name: rosjava
+    local-name: rosjava_core
     uri: https://rosjava.googlecode.com/hg
     version: default

docs/src/main/sphinx/index.rst

@@ -26,6 +26,7 @@ Contents:
    :maxdepth: 2
 
    overview
+   installing
    building
    best_practices
    getting_started

docs/src/main/sphinx/installing.rst

+Installing rosjava_core
+=======================
+
+rosjava_core should be installed using rosws. See the `rosws tutorial`_ for more information.
+
+.. _rosws tutorial: http://www.ros.org/doc/api/rosinstall/html/rosws_tutorial.html
+
+The following instructions configure rosjava_core for electric on Ubuntu.
+
+#. sudo apt-get install easy_install
+#. easy_install --prefix ~/.local -U rosintall
+#. cd ~/my_ros_workspace
+#. rosws init
+#. rosws merge /opt/ros/electric/.rosinstall
+#. rosws merge http://rosjava.googlecode.com/hg/.rosinstall
+
+Don't forget to source the appropriate new setup shell script.
+

rosjava-dev.rosinstall

-- svn:
-    local-name: ros
-    uri: https://code.ros.org/svn/ros/stacks/ros/trunk
-- svn:
-    local-name: ros_comm
-    uri: https://code.ros.org/svn/ros/stacks/ros_comm/trunk
-- hg:
-    local-name: rosjava
-    uri: https://rosjava.googlecode.com/hg
-    version: default