Semi-major update to the settings GUI
Semi-major update to the settings GUI

- Changed the settings GUI to remove start button and make it only
appear at the end.
- Provided tooltips and better instruction on how to use the GUI
- Performs input error checking between each frame rather than at the
end.
- Removed unnecessary functions now covered by classes in gui_utils
- Fixed issue with backslash appending to spectra path. Now using
forward slash to be compatible with mac and windows.

BU-hammerTeam/PyHammer