Create the concept of enabled plugins

This allows users to disable a plugin without completely removing it.
Instead, they simply remove the `plugins/enabled/*.bash` file for the
plugin they want to disable.  This continues the concept of "everything
on" while providing greater flexibility to future users.

It might be a good idea to allow turning these off by default in the
future and allowing not only the `plugins/enabled/*.bash` files but also
an array of `<plugin_name>` values that would search for
`plugins/available/<plugin_name>.plugin.bash` to enable them.  That
method would make it easier for people custom tune their plugins from
within their `.bash_profile` script.

plugins/available/javascript.plugins.bash

@@ -0,0 +1,17 @@
+#!/bin/bash
+#
+# The install directory is hard-coded. TOOD: allow the directory to be specified on the command line.
+#
+
+
+function rails_jquery {
+  curl -o public/javascripts/rails.js http://github.com/rails/jquery-ujs/raw/master/src/rails.js
+}
+
+function jquery_install {
+  curl -o public/javascripts/jquery.js http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js
+}
+
+function  jquery_ui_install {
+  curl -o public/javascripts/jquery_ui.js http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/jquery-ui.min.js
+}