Fix the way LinkSuggest time measurement keys are generated

Changing newrelic measurment key for link suggest:
Custom/getLinkSuggest\sql-1/[seconds|call] - > Custom/getLinkSuggest/sql-1[seconds|call]

To avoid this kind of confusion in future I've added possibility of passing key as array of parts instead of full imploded key
i.e. you can pass ['x','y', 'z'] instead of 'x/y/z'.

@jacekjursza @federico-lox