Merge topic 'externalproject-cleanup'

3351b7b82c ExternalProject: Reformatting only
691f0c7612 ExternalProject: Minor cleanup to use more convenient commands
b4db306aff ExternalProject: Remove unused property docs
5c021c8355 ExternalProject: Replace SEND_ERROR with FATAL_ERROR

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !7285