attach use context current block instead of block num passed as a parameter
- change attach interface, passing a block num is no longer required, context's current_block_num is taken instead
- remove the procedure for detaching contexts
- fix live sync test to deal with WAL
dependant applications MRs : hivemind: hivemind!662 (merged) btracker: balance_tracker!74 (merged) hafbe: haf_block_explorer!152 (merged) hafah: HAfAH!114 (merged)
Edited by Bartek Wrona