Based largely on @richardpiazza work in #945

This PR updates the Swift Package.swift file to the tools version 5 format.
And adds support form missing mobile content product

Along with that change, the minimum supported platforms are added (using platforms: []), and the supported language versions are listed (using swiftLanguageVersions: []).

Due to now listed the minimum os support, files in ProcedureKitCoreDataTests needed to have a '@available' attribute applied making sure the tests where only run on supported platforms. (Primarily due to the use of NSPersistentContainer).

Also, since some build environments may not understand what an .xcdatamodeld file is, I've added the TestEntity class definitions, as well as, creating the NSManagedObjectModel definition in code. This allows the tests to run and pass while using the swift test command.

These updates were tested with Xcode 11.1 using swift packages.
(Could relate to #939)

@danthorpe There's and issue i haven't managed to resolve with the Location target:

The pointer address passing doesn't work with swift 5, this needs to be addressed before merging the PR, maybe you can take a look at this, frankly i'm a bit stuck here

internal extension CLLocationManager {

    static func make() -> CLLocationManager {
        fatalError("FIX THIS")
//        var manager : CLLocationManager
//        performSelector(onMainThread: #selector(make(new:)), with: &manager, waitUntilDone: true)
//        return manager
        // return DispatchQueue.onMain { CLLocationManager() }
    }
    
    @objc static func make(new manager: CLLocationManager) {
        fatalError("FIX THIS")
//        manager = CLLocationManager.init()
    }
}