Allow passing a message to tryCompare

Also adds a check to make sure timeout is a number, for people
that are moving from compare() to tryCompare() and forget of the extra
timeout parameter

Change-Id: I54e56e2014c022e06622edebca1fd36172c75009
Reviewed-by: Yunqiao Yin <charles@mazymind.com>
Reviewed-by: Caroline Chao <caroline.chao@digia.com>
Doc: Updated Qt QML and Qt Quick module pages.

-added \qtvariable
-added Qt QML to the modules group

Change-Id: I524bbcea501b7ab5ea49482de0119e3e6d630065
Reviewed-by: Martin Smith <martin.smith@digia.com>