Before the count was reset every time process was restarted.
Also add 'db' label to distinguish between waku and whisper DBs.
Signed-off-by: Jakub Sokołowski <jakub@status.im>
This commits adds support for postgres database.
Currently two fields are stored: the bloom filter and the topic.
Only the bloom filter is actually used to query, but potentially we will
use also the topic in the future, so easier to separate it now in order
to avoid a migration.