Author: Bas Brands
MDL-62757 themes: validate theme preset files
Preset files need to be validated to ensure compiling SCSS does not
break.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=8040fafaa8e06d611ae6eb8320bbec5de26466f2
http://github.com/moodle/moodle/commit/8040fafaa8e06d611ae6eb8320bbec5de26466f2
+ 3.8 en [invalidthemepreset,core_admin]