Create an easy way to setup a WITSML Gateway

Child of #250
Currently, to setup a WITSML gateway, sysadmin has to use the command line and perform a series of steps manually. However, as Tempus moves to a SAS model, This may not be possible for a variety of reasons and role of setting up WITSML gateways (and other gateway too) will shift to the Tenant Administrator.

We therefore need an easy way (from UI) for a Tenant Admin, which will work as follows:

1. Add a sidebar entry called 'Gateways' available only to Tenant Admins.
2. This will lead to a set of screens, where Tenant Admins can configure

- Tempus Gateway - inputs host, port, size, gateway token etc
- Device Gateway - inputs name, gateway access token, attributes
- Extensions - similar to existing function under Device Tab

3. Upon Save and Confirmation, we will configure Tempus Gateway, deploy it in a Kubernetes cluster and also setup the required extensions.

4. Gateway devices will NOT be listed in the Devices tab. This will also ensure that Bob Jones doesn't make accidental changes to them.