(Update) Using of different events for different actions

[varasev]

Several events contain a string field which encodes the actual reason of the event emission, such as action in KeysManager:

event MiningKeyChanged(address key, string action);
event VotingKeyChanged(address key, address indexed miningKey, string action);
event PayoutKeyChanged(address key, address indexed miningKey, string action);

action is not arbitrary: it can take only three different values: "swapped", "added", and "removed".

This means that, every time these events are emitted, some more gas is consumed to send the string along, and an event listener has to match the action field against these three values to really know what happened. It seems that we could instead use different events for different actions. E.g.:

event MiningKeyAdded(address key);
event MiningKeyRemoved(address key);
event MiningKeySwapped(address key);