Hide section for partition resizing when not needed

[martignoni]

Followup of #45. We'll hide the section when the SD card was already resized to its max sized.

[martignoni]

This will function correctly only with such a line in /etc/sudoers file:

www-data ALL=(ALL) NOPASSWD:/sbin/parted /dev/mmcblk0 unit MB print free

[martignoni]

See commit 1e35aec.

[martignoni]

Testing done.