Added block and account validation scripts

Added scripts/validate_blocks.php and scripts/validate_users.php.

validate_blocks is useful for coin's that can fork-fest (like catcoin lol) and frequently create incorrect fork mined blocks. The script validates all the blocks in database against the coind and outputs them. It's also aware of orphan blocks and doesn't report them for so.

validate_users.php filters out accounts that didn't logged in since $timeLimitInDays and print's useful information about them. 
* The last login unixtime stamp
* Days since last login
* Does account have any assigned transactions?
* Balance
* Is the account stale?