shell: Add input space validation when adding a server

Add input validation and visual style when error occurs.
Avoid resizing the dialog when error messages show up.
Remove get_focus and lose_focus functions.
Add some restrictions for empty host name in case "Next" button is enabled accidentally.

Fixes #943
Closes #957
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Remove extra spaces in cockpit-setup.js

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Moves realm leave error message and changes its color

Moves error message below the leave button and changes text color to red

Fixes: #934
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Creates hover effect for server avatar

Fixes: #868
Closes: #972
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Hide link local IPv6 addresses on the network overview page

Fixes #800
Closes #975
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Put network interface name in a more prominent place

Fixes #799
Closes #976
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Discover default domain and show it as a hint

Closes #978
Reviewed-by: Stef Walter <stefw@redhat.com>
Release version 0.19
WIP: Show bridges.