Squash ios crash log symbolication

To realize iOS/OS X full stack symbolication, the changes introduced here must be combined with the changes in github.com/ferrerod/cocoa also. Two symbolication scenarios are supported. If installed on OS X, it will symbolicate in-line (upon receipt of the crashlog from the client). If not installed on OS X, the script/squash_symbolicate_ios_crash, lib/squash_ios_crash_log_symbolication.rb, and config/database.yml and config/symbolication_paths.yml should be copied to an OS X machine with Xcode, plcrashutil and ruby environment available. In that scenario, the script is run ad hoc or as a cronjob to symbolicate the crashes on a regular interval.