dissallow deletion of core package
dissallow deletion of core package

Microsoft/pxt,switchinnovations/pxt,switchinnovations/pxt,switch-education/pxt,switchinnovations/pxt,Microsoft/pxt,switchinnovations/pxt,Microsoft/pxt,switch-education/pxt,Microsoft/pxt,switch-education/pxt,switch-education/pxt,playi/pxt,playi/pxt,playi/pxt,Microsoft/pxt,playi/pxt,switch-education/pxt