Remove isActive from the StorkNode and StorkContract structs

[shankars99]

bool isActive is not needed

Incase of a StorkNode if the node misbehaves

1. storkNodes[_storkNodeAddr].stakeValue can be set to 0
2. storkNodes[_storkNodeAddr].stakeEndTime can be set to block.timestamp

As a StorkContract can't misbehave

1. just set storkContracts[_storkContractAddr].txCount can be set to 0