Don't restrict autocompile intervals to integers

[enterprisey]

In this dialog: I don't see why the smallest supported interval is 1 second. Sometimes I want to autocompile every half a second, or even a quarter of a second.

Can support be added for that?

(In response to the objection that a single compilation might take longer than the interval time, we can just follow the current behavior (not sure about this) and not start a new compilation once one is already running.)

[SalathielGenese]

Give try to 0 or even 0.5?