Feature request - memfs mount due to fast SD card wear on rpi device.

[a1j]

RRD database is very hard on SD cards and will wear them out completely in less than a year.
But data is not that big and RPI has enough RAM to put those files on tmpfs. Therefor the suggestion:

1. mount tmpfs in /var/lib/pymc_repeater.tmpfs (add tmpfs /var/lib/pymc_repeater.tmpfs tmpfs defaults,size=100m 0 0 to fstab).
2. create symlink to repeater.db and metrics.rrd pointing to tmpfs
3. in a shutdown script add a command to preserve tmpfs contents in pymc_repeater.preserve
4. in a startup script add a command to restore tmpfs out of pymc_repeater.preserve