WithGlobalDom is the same as withReactDOM, remove duplicate

...and put it in a more organized spot on filesystem.
...and copy over the improvement tweaks we did to it

Change-Id: I5b406c36efecc8e522ad6f7f95e7bf475fdd6171
Reviewed-on: https://gerrit.instructure.com/38088
Reviewed-by: Sterling Cobb <sterling@instructure.com>
Product-Review: Sterling Cobb <sterling@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Ryan Shaw <ryan@instructure.com>
QA-Review: Ryan Shaw <ryan@instructure.com>