shell: Implementing searching and pulling docker images

Fixes #373
Fixes #370
Signed-off-by: Stef Walter <stefw@redhat.com>
 * Fixed whitespace issues
shell: Move some docker pull related things around

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Add docker pull tag text field

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Show docker pull errors and tag text

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Fix styling and placement of docker pull tag field

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Styling for active docker pull class

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Mark the selected row as active in docker pull dialog

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Show more progress and use the .stream and .done callbacks

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Make only downloading docker layers show

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Fix image location in docker pull

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Remove the docker download_fail event

Closes #600
Reviewed-by: Stef Walter <stefw@redhat.com>