checkbox-touch: remove option to go back from resume-screen

This patch makes CBT clear pagestack when resume screen is displayed.

Fixes: https://bugs.launchpad.net/checkbox-touch/+bug/1399304
Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
"automatic merge of lp:~kissiel/checkbox/fix-1399304/ by tarmac [r=zkrynicki][bug=1399304][author=kissiel]"
checkbox-touch: disable select/deselect all actions when selecting one thing

This patch makes selection screen not show select all and deselect all actions
when selection is done in 'select only one' mode.

Fixes: https://bugs.launchpad.net/checkbox-touch/+bug/1399607
Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
"automatic merge of lp:~kissiel/checkbox/fix-1399607/ by tarmac [r=zkrynicki][bug=1399607][author=kissiel]"