Add support for pagination of errors

Previously errors could only be listed as all errors since a given time.
Now this is augmented with the ability to paginate the list, and show
only a certain range of errors.

This change is as-yet untested.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit
Add clear_errors API call

Create a new API call to remove some set of errors from the log.
net votes -> approval
Fix some typos in API call documentation
Include block numbers in exported fork graphs
Make start and end block numbers inclusive in blockchain_export_fork_graph
fix for duplicate transaction bug that causes forks
test case that registers a named account in the blockchain as a potential delegate
Merge branch 'approval_voting'
restore importing private key without name
Fix delegate block production loop
Merge branch 'master' of github.com:BitShares/bitshares_toolkit

Conflicts:
	libraries/blockchain/include/bts/blockchain/config.hpp