Fixed some layout issues.
Changed the theme to display the status bar (no fullscreen as it was by error).
Changed some labels, var names and strings.
Added a new string item to calculate_tip_options
Fixed an issue with the results section, the total to pay value was not aligning to the right.
Code refactored to introduce the Engine class into the process.
Reduced the label text length to allow the widgets to grow a little more for smaller screens.
Changed textboxes text hint color.