Strongly-typed events

[vitaly-t]

In relation to #3908, #3904, #3827 and #3539, plus general TypeScript makeover...

I was recently struggling with events in my own project, and ended up writing my own module to handle events, in case it is of any interest here.

Since you are transforming into TypeScript, strongly-typed events is a must-have.

[vitaly-t]

v0.7.0 added very useful diagnostics, to help counter memory leaks and performance degradation.

[shuse2]

Closing this issue since value added is small, and mostly already implemented