ENH: Add option to disable Qt in InitCMakeCache

The new build scheme allows most of TubeTK to be built without Qt, but
InitCMakeCache.cmake seems to override the default option when running a
dashboard script.

Change-Id: I2e458a26ba37711e3472cc86c674235e502bb1bd
Merge topic 'QtOptionInitCMakeCache'

2fa2424 ENH: Add option to disable Qt in InitCMakeCache