Refactored Google Chart to load async JS lib async

The Google Chart library is now loaded on demand when clicking on the
template debugging tab.

- modified:   system/expressionengine/third_party/ee_debug_toolbar/ext.ee_debug_toolbar.php

Added template debug JSON data to view payload

- modified:   system/expressionengine/third_party/ee_debug_toolbar/libraries/Toolbar.php

Added method to construct a JSON object from the template log data
for use by the chart JS

- deleted:    system/expressionengine/third_party/ee_debug_toolbar/views/tmpl_graph.php

Removed the template graph view since the JS has been moved to its own JS file.

- modified:   system/expressionengine/third_party/ee_debug_toolbar/views/toolbar.php

Removed tmpl_chart view loading and added data object containing
template logging JSON data that can be used by the chart library

- modified:   themes/third_party/ee_debug_toolbar/css/ee_debug_toolbar.css

Added a minimum height to the EEDebug_chart so that the tab slides
open to the correct height and also showing a loading indicator
while the chart is initialising

- modified:   themes/third_party/ee_debug_toolbar/js/ee_debug_toolbar.js

Updated to dynamically load the Google JSAPI as well as our own
js file to handle the chart construction

- new file:   themes/third_party/ee_debug_toolbar/js/ee_google_chart.js

All Google Chart from thetmpl_graph view has been refactored and
moved to this standalone file. Also includes a JSAPI load event
handler