Auto-detecting tracetemplate path

This resolves some issue people have been experiencing with the npm installed or .app versions of appium where the XCode 4.6 Automation.tracetemplate is being used with XCode 5. We now just use the one bundled with the currently selected version of XCode.

A flag has been added to supply a custom tracetemplate in the event someone wants to add extra instruments to the trace or if for some reason auto-detect doesn't work with their xcode setup (this may happen on XCode 4.1 or any other 2.5+ year old version of Xcode)

We also no longer bundle Automation.tracetemplate files with Xcode