shell: Polish Create Volume Group dialog

Add Warning when no available disks
Validate the length and content of input
Add Visual style when error occurs
Check the precondition of creating a volume group
Disable the create button properly

Fixes #871
Closes #981
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Redesign the login tab of Add server dialog.

Make the form of login tab similar with Chang host name dialog
Apply proper visual style and show error message when error occurs
Disable the Next button appropriately

Fixes #950
Closes #1022
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Remove unused code from journal page

The search code is no longer in use and is rather complicated to
maintain going forward. The serivce filtering is not used by the UI
but is a vital part of tests: simplify it.

Add tag based filtering (ie: logger --tag) which is also used
from integration tests, and not exposed in the UI.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Pass a string or array as command for cockpit.spawn

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Implement a journal loading based on journalctl

Use journalctl to load and then follow the journal, by having it
output json and send it to us.

Fixes #850
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
daemon: Remove journal Query code from cockpitd

Closes #989
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>