Initial window improvements, reveal and reset master password.

[FIXED]     Initial intro window didn't always show up reliably.
[ADDED]     Ability to temporarily reveal master password while typing it.
[IMPROVED]  When you go down the sites list, fade out the fade-out gradient to prevent the selection from becoming invisible.
[ADDED]     Ability to reset your master password.
[UPDATED]   Initial screenshot of Master Password for Mac and iPhone.