Reduce loadingtime of XmlMaterialProfiles by 25%
Reduce loadingtime of XmlMaterialProfiles by 25%

XmlMaterialProfile did a lot of findInstanceContainers() by GUID and base_file. If base_file is always set, matching GUID is superfluous.

This shaved off 20% loading time of the application (43 vs 34 seconds) on a cached load.

fieldOfView/Cura,ynotstartups/Wanhao,Curahelper/Cura,fieldOfView/Cura,senttech/Cura,ynotstartups/Wanhao,totalretribution/Cura,totalretribution/Cura,hmflash/Cura,Curahelper/Cura,hmflash/Cura,senttech/Cura