Encode certs and keys so they can be handled by NVRam backup/restore routines.

These routines cannot handle ASCII values below 32 (such as CR or LF), which was
causing restoring settings from a backup file to fail when you had OpenVPN or
multiple SSH authentication keys configured.  We now filter our LF, and replace
CR with a ">" character.

Note that this change will slightly break backward compatibility with
previous FW versions - people downgrading will have to correct their OpenVPN and
SSH authkeys.  A simple text editor search and replace will do the job -
have to replace ">" with end of lines in all those fields on the webui.
Merge branch 'master' of github.com:RMerl/asuswrt-merlin