flexible and friendly power.ACE.test

[tbates]

• [x] nice graphic for help
• [x] references
• [x] power to detect a (or c)
• [x] set value of path to be dropped, AA, CC
• [x] settable MZ_DZ_ratio
• [x] user-friendly reporting: no unused columns, overly precise data, ambiguous n (pairs? total?)
• [x] method ("ncp" or "empirical") and search mode supported.
• [x] Robust input error checking, smart switching of modes.
• [x] Add tryHard and optimizer options

power.ACE.test(AA = .5, CC = 0, update = "a") 

 method = ncp
        n = 333
    power = 0.8
sig.level = 0.05
statistic = LRT