MDL-41476 scorm admin settings & scorm12.js - SCORM 1.2 standard mode and changing CMIString length

Adding SCORM 1.2 standard mode checkbox in scorm admin panel. By default it will be enabled
(i.e: config name = `scorm12standard`, plugin name = `scorm`, value = `1`)
If `scorm12standard` is `1` CMIString256 is of length 256 and CMIString4096 is of length is 4096
if `scorm12standard` is `0` CMIString256 and CMIString4096 are of length is 64000