Lots of small changes

* name_scan help was showing name_history text
* typo channles -> channels
* --version --help and RPC help now working
* coinexplorer names added
* --noirc added and --notify now working
* more checkpoints
* purge depth on first run not showing warning
* more dns seeds
* coinexplorer after readBlockFile now sets persistance correctly

* using persistence with an e everywhere