Add a settings/preferences view

[tasermonkey]

With the addition of the option for displaying usernames as described in https://github.com/passwordmaker/android-passwordmaker/issues/19, I think the app is finally needing a preference.

The preferences I have so far are:

• Save master password hash
• Save Inputs for N minutes
• Display Username field

[tasermonkey]

This was implemented in change https://github.com/passwordmaker/android-passwordmaker/commit/341ab6d82371d16be39f396e3a79b6675a3084d4