Added blockhash solution checking
Added blockhash solution checking

Stratum of @moopless supports blockhash as a solution. Check for that
one first.

Addresses #405

nimblecoin/web,UNOMP/chunky-mpos,shreeneve/test,mculp/chunky-mpos,sixxkilur/php-mpos,UNOMP/chunky-mpos,BlueDragon747/php-mpos,MPOS/php-mpos,shreeneve/test,CoinHashMe/MPOS-SSO,CoinHashMe/MPOS-SSO,bankonme/php-mpos,bankonme/php-mpos,sasselin/xcoin-mpos,ychaim/php-mpos,nimblecoin/web,studio666/php-mpos,studio666/php-mpos,xisi/php-mpos,machinecoin-project/php-mpos,sixxkilur/php-mpos,mmitech/php-mpos,UNOMP/chunky-mpos,shreeneve/test,MPOS/php-mpos,CoinHashMe/MPOS-SSO,mculp/chunky-mpos,CoinHashMe/MPOS-SSO,ychaim/php-mpos,ychaim/php-mpos,xisi/php-mpos,machinecoin-project/php-mpos,mculp/chunky-mpos,sasselin/xcoin-mpos,MPOS/php-mpos,mmitech/php-mpos,sasselin/xcoin-mpos,studio666/php-mpos,evgenyponomarev/pool,bankonme/php-mpos,UNOMP/chunky-mpos,mmitech/php-mpos,nimblecoin/web,BlueDragon747/php-mpos,machinecoin-project/php-mpos,evgenyponomarev/pool,mculp/chunky-mpos,sixxkilur/php-mpos,xisi/php-mpos,evgenyponomarev/pool,BlueDragon747/php-mpos,CoinHashMe/MPOS-SSO