add estimation of efficient time till reset

Calculated in terms of how many more heavenly chips to earn. This is based
on the work done on the Cookie Clicker subreddit
(http://www.reddit.com/r/CookieClicker/comments/1wrudk/a_theoretical_analysis_of_when_should_i_reset_in/).

The basic formula is to reset when

M*cps*T - C = (1/2)h^2 where:

M = effective multiplier
cps = current cps divided by one trillion
C = cookies baked (this game) divided by one trillion
T = time in seconds since session started
h = number of heavenly chips you'd gain if you reset now

I re-arranged this formula as:

Number of heavenly chips left to earn until resetting is more efficient:

h = sqrt(2*M*cps*T - 2*C)

I used effectiveCps() function instead of M*cps, as this seemed like the
best calculation.

I also updated the FC button to display both of these quantities. No
automatic resetting has been added, so it is up to the user to track these
quantities.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>