feat(modal tooltip): Adds a feature to allow for custom name-spacing of events

This feature changes the events namespace from using options.prefixClass to options.prefixEvent. I found the need for this when I had multiple modals on the same page and wanted to do some tasks on the hide event. Using options.prefixClass also changes the classes so I couldn't continue to use the default styling, adding this option allowed me to watch for the hide event for specific modals only.

Change the use of `prefixClass` to just be used for class prefixes. Added a new option called `prefixEvent` for prefixing the events.
Allows for seperate prefix for events across multiple modals whilst not changing the classes allowing for more customisation.
Fix an error on tipElement that occurs when using the dropdown directive with a dynamically changing object as the source.

Fixes up the previous PR #636