Create welcome content for Application Explorer view

[dgolovin]

[dgolovin]

@gorkem Going to show ^ that as Welcome page for App Explorer when empty, do names look good or it should be something without 'K8s' and 'OpenShift'?

Could be:

• Login
• Change context
• Provision a Cluster

[gorkem]

How about we align things a bit more

• Login
• Select Kubernetes Context ## Align "Switch Contexts" command with this.
• Add OpenShift Cluster ## This aligns with the webview's title.

[dgolovin]

I agree on both changes, so it is going to look this way (see updated screenshot above).