additions to .irbrc for a better irb experience
WIP should have a good tool for working with Xcode
deprecate Core.xcode_version with XCTools.xcode_version
Core.default_tracetemplate should always select _Xcode_ tracetemplate

handles edge case where Automation.tracetemplate could be present in
the user's Instruments/Templates applications support directoy.
Core.udid_and_bundle... should use XCTools for version checking
run_loop_spec should use XCTools