Allow Querying Version

[NWPlayer123]

It would be nice if build scripts could check the objdiff version without relying on the user, especially if they provide the program instead of e.g. dtk-template downloading it for them. An easy way to solve this is that if objdiff is ran with --version or -v, don't try to load the gui and just print out the version to stdout, for build scripts to grep against.