Always stop timers when exiting the 'Timer.time' block

[kjrokos]

Previously, throwing an exception inside the Timer.time() function block would cause the running timer to continue outside of the block.

This change does two things:

• When the block exits for any reason, the timer will stop
• Adds a @Throws annotation to the function block so Java code calling this method is also allowed to throw checked exceptions. Previously Java code could only throw unchecked exceptions, while Kotlin code was able to throw any exception. This brings the functionality closer to parity.

Resolves #361

[TrueFiskibility]

Looks good. Note that Java code was always able to throw unchecked exceptions, but it wasn't able to throw checked exceptions. I suppose the choice to allow checked exceptions is a matter of design; I have no opinion on it.