Allow simplenews to be re-installed after uninstalling it

Problem/Motivation

It is currently quite hard to install simplenews again if you uninstalled it. Especially when developing, that's very annoying.

Proposed resolution

I made the following changes to make that easer:
* All simplenews node type configuration is moved to optional. We don't really require it I think and then we simply re-create what we need when re-installing the module. We don't want to force-delete the data when uninstalling, so we allow that node type to not be deletd.
* Added an enforced dependency on simplenews on the view modes that we add. Those make no sense without the module, so they should be deleted
* Also contains some performance improvements in regards to config schema in simplenews_install().

This possibly fails due a core bug, lets see.

Remaining tasks

User interface changes

API changes

Data model changes