Since plenty scrypt based currencies are supported, changed error
message to say `wallet` instead of `litecoind` when failing to connect
to RPC service.
* Currently no GUI, use DB access to change the row entry
* Upgraded Database table `accounts` with upgrade SQL
* Updated `admin` field to `is_admin` as boolean
* Modified pages, classes, templates to support is_admin and is_locked
Addresses #147