Removes vchDefaultKey which was only used for first run detection.
Improves wallet first run detection by checking to see if any keys
were read from the database.
This will now also check for a valid defaultkey for backwards
compatibility reasons and to check for any corruption.
Keys will stil be generated on the first one, but there won't be
any shown in the address book as was previously done.
This commit adds basic keypool mark-used and topup:
- try to topup the keypool on initial load
- if a key in the keypool is used, mark all keys before that as used and
try to top up
This commit moves functions start_node, start_nodes, stop_node and
stop_nodes functions into the BitcoinTestFramework class. It also moves
the bitcoind_processes dict and coverage variables into BitcoinTestFramework.
