shell: Patternfly error styling for host name dialog

Adds patternfly has-error class to input box and error message when an
error is present. Also fixes grammar in error message slightly and
removes unneeded cockpit-note class.

Fixes #1029
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Error flags and restricts long input for host name dialog

Adds another error message, highlights input box, and disables change
botton when the pretty Real name input is longer than 64
characters. Displays seperate error messages for too long real host
name input and the use of special characters. If the user causes a
second error the second error will be shown below the first.

Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: More descriptive labels in change host name

Fixes #1034
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Selective way of copying host name input

Will only copy first 64 characters of pretty host name to real host
name. This is done to avoid throwing a character limit error. Also
changes the way we call our update method when typing in the host names.
Now updates on input rather than on keyup.

Fixes #1035
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>
shell: Disables host name change button when necessary

When there is no input in either change host name input boxes the change
button becomes disabled.

Fixes #1036
Closes #1030
Reviewed-by: Marius Vollmer <marius.vollmer@redhat.com>