Make soft keyboard handling consistent with RedPotion

[darinwilson]

PMScreenModule currently has soft_input_mode and hide_keyboard, which are leftovers from BP's embryonic stage. We should try to harmonize these with RedPotion.

[jamonholmgren]

Note: RMQ has rmq.app.hide_keyboard already (app.hide_keyboard in RP).

infinitered/rmq#234

[skellock]

show_keyboard is now available because unlike iOS, simply placing focus in a UIResponder is not enough to raise the keyboard (perhaps this is simulator only issue?).

Also, thx for adding soft_input_mode @darinwilson. We're now using that + layout_weight on one of our screens to ensure the screen layout is consistent with the keyboard both up & down.

[darinwilson]

👍