Don't munge memo on issue/create of assets, set issuer account

The scanners were replacing a meaningful memo on issue/create asset
transactions with a canned one. Fix this so that the memo is left alone
if it's already set.

Also, the from account was left empty on issue transactions, but the
from account must be the issuer (no one else can issue that asset) so we
can actually set it.
Minor cleanup in wallet::add_contact_account

Make assert failed exceptions human readable, and also don't overwrite
the old private data if the new private data is null.
fix scanning for market issued assets
Merge branch 'master' of github.com:BitShares/bitshares_toolkit
Accelerate block prop with async revalidation.

Adding a mutex to prevent push_block from being reentrant as the first
step toward making the network code run in its own thread.
[gandalf] Added modified config and batch for win32 build under Jenkins.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit

Conflicts:
	libraries/wallet/wallet.cpp
Add wallet_scan_transaction command
Fix list_errors_brief
Make message_oriented_connection clean up its async tasks on destruction
Dump the status of all p2p connections to the p2p log every minute
Cancel accept/connect tasks when destroying a p2p connection object.
Set remote_endpoint earlier to improve logging of disconnected incoming connections
Update FC submodule
Update FC submodule
Resolve #457: Extend blockchain_list_accounts to allow numerical
pagination

Previously blockchain_list_accounts only allowed pagination by
specifying a name prefix to return results after. Now it supports taking
a number in place of the name and returning a list of accounts starting
at that index.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit
Add a new common script with reduced number of delegate keys for test clients that scan the blockchain. wallet_asset_test is currently passing locally on my system, but we probably need to disable transaction id display and the like (e.g. signatures) for test comparison purposes.
Merge branch 'master' of github.com:BitShares/bitshares_toolkit
increasing block rate and size for dryrun 8
add pre-registering market pegged asset