Make UI agnostic of epinio's namespace and other improvements

[richard-cox]

Summary

Fixes #322

Occurred changes and/or fixed issues

• Epinio can be installed to namespaces other than epinio
• This PR remove's the hardcoding to epinio and discovers it instead by ns of the epinio-server pod
• Also
  • Make home page link to cluster explorer's home page into a true anchor
  • Add a link to take user from an epinio application to cluster explorers deployment detail page

Areas or cases that should be tested

• Embedded world - Discovery of epinio instances
• Embedded world - Metrics link on home page
• Embedded world - Link from App to Explorer Deployment Detail page

[torchiaf]

LGTM, added a small fix to exclude local cluster from epinio instances table

[torchiaf]

local cluster is listed as epinio cluster but it isn't:

In a first round, I assumed local cluster had to be removed from the list, but given PR 366 , I think there is a bug in ingresses/namespaces calculation in discover() function.

Edit:

The instances table works fine in a clean environment! I'll approve it.

[torchiaf]

LGTM