Allow changing the container environment at runtime

[insidegui]

It is sometimes useful to be able to use the production environment in a debug build to test something. Currently, the environment is set to .development automatically for debug builds, and to .production for release builds, which I think is a great default, but it would be neat if the user of the library could override that manually if they want to.

If the idea is to replicate the CloudKit framework more closely, then this change could be provided at compile time with a flag different from DEBUG, which would take the place of the entitlement in the original framework.

Updated by Eric:

• Dynamic environment selection via initializer
• Dynamic environment selection via configuration

[edorphy]

I added environment as an initializer parameter for now. Eventually I'll add another constructor that takes in a configuration that can grab from the plist.

[edorphy]

Added to CKWSContainer.Configuration in 1c3d317

Closing out.