Block indexing is not retroactive #14
Description
During the syncronisation of explorer I've initally run spaced without --block-index, and the explorer didn't sync any of the blocks. Later rerunning spaced with --block-index did not help, however deleting the data dir of spaced and running with block index from the start solved the problem.
It seems that indexing is not retroactive, however I'm not completely sure. Probably it adds indices only to the new blocks, but does not touch the older ones.
Perhaps it would be nice to raise an error or resync if the indexing is enabled.