Light indexing mode

> Note: the pre-v2 version supported a "light" indexing mode for personal use, where less data is kept on-disk in exchange for a performance hit and more reliance/load on bitcoind. This option is not currently available, but can be enabled with an older esplora release. We're hoping to eventually get this feature back. Let us know if you find this important!

I would like this light indexing mode back, I had been using the pre-v2 version fine and then upgraded but haven't been able to use it yet, it has been indexing for over a month now and today it's at blk01160.dat, not sure if it will ever catch up, I think I'll have to abort and downgrade for now.