Replaced --low-ram flag with --write-every
Replaced --low-ram flag with --write-every

In this big commit the --low-ram flag gets replaced with --write-every, which
receives a number. If that number is 1, no cache will be used, otherwise it's
used to write down to disk and clear RAM cache after that many tracks are
indexed.

maurodelazeri/shiva-server,tooxie/shiva-server,tooxie/shiva-server,maurodelazeri/shiva-server