For the new attribute "onload_delay", reading and transfering it into testcase JSON format.

This attribute will be used in webpage for delaying to check result after "onload" event
Update test_definition schema to 1.0.2-1

-- version 1.0.2-1 --
1\ add a new int optional attribute "onload_delay" with default "3"
Merge pull request #21 from Shao-Feng/onload_delay

Onload delay PR