Refactor graph_page_data

Remove mean function

Add comments for refactor.

Add more comments

Add more comments, refactor GetMedianRun, and make successfulOnly a required parameter to values.

Add test to graphPageDataTest.php

Add test to graphPageDataTest.php

More documentation

Move GetQuantiles and GetNumeric to graph_page_data.inc

Finish moving GetQuantiles and GetNumeric to graph_page_data.inc

More updates to test

Test pageload data error

Merge some changes from https://github.com/geening/webpagetest/commit/936dba606a072f26b727b3fcbf96bfc0620c842a

Update test load page data

removing test_load_page_data

Code cleanup of graph_page_data.php

Add GetMedianRun test

Fixing code review issues in https://codereview.appspot.com/100870045/

Refactor graph_page_data.php to make it easier to combine multiple tests
onto
one chart.
Show median metric value in addition to median run.
Extract commonly used functionality in page_data.inc into "values" and
"successfulRun" functions.
Fix some typos and add comments.

Remove values corresponding to failed runs from tests -- see differences
at
http://latencylab/graph_page_data.php?test=140529_V9_35C
http://latencylab/graph_page_data.php?test=140530_NR_318
Added an embedded Chrome trace viewer
Added a cache for the processed dev tools requests and page data so we don't keep re-processing the large dev tools files.