Better macOS bundling

[marceloexc]

now cmake will create a nice portable abaddon.app that could then be dragged to Applications/ folder.

directory for resources now lives inside of the .app/, so it now would go to Contents/Resources/, instead of having to go alongside the executable. also has a cmake option for users to turn off the bundling and only compile a standalone executable if they want to

[marceloexc]

in the future #263 would benefit from this too