Change checking logic of Start-Up Activities.

- implement a check in the MainActivity that will check only for the
  CURRENT_MONTHLY_BUDGET key, which is set in the last round of start-up
  activities in all versions. Therefore, if it's set that means it's not a
  new user in versions prior to 1.2.0 and it's not a new user in 1.2.0
  version also, since it's the last key to be set in start up activities.
Refactor code in SettingsActivity

Remove butterKnife injects and refactor the code a little in
SettingsActivity.
Modify the layout for different resolutions

- Add necessary changes to layouts for differents screen densities.