added interface for tooltip functions
added interface for tooltip functions

openspending/openspendingjs,RCGTDev/openspendingjs,openspending/openspendingjs-old,RCGTDev/openspendingjs,RCGTDev/openspendingjs,openspending/openspendingjs-old,RCGTDev/openspendingjs,openspending/openspendingjs,openspending/openspendingjs,openspending/openspendingjs,openspending/openspendingjs-old,openspending/openspendingjs-old