Gravity: Fixup scroll bar range

Gravity: remove extra spaces

Gravity: Live update settings and cleanup

Now that this screensaver shows a preview, update the settings live
so that the display updates immediately.

Since this didn't work before this screensaver took a shortcut and only
updated the settings when the saver started.

Some other changes include:
* Update copyright header, add myself to the authors list.
* Convert Particle from using a BList to a BObjectList and remove casts.
* Use switch statement to set particle color that has a default case for blue.
* Initialize member variables to a default value in the constructor.
* Remove Constants.h, the remaining constants are in ConfigView.cpp
* Convert deprecated GroupLayoutBuilder to a LayoutBuilder template instance
* Convert GravitySource from a class to a struct since all members are public.
* Simplify realCount calculation to just a single left shift.
* A bunch of style fixes
- lots of whitespace fixes
- rename rect to frame in GravityView and ConfigView
- reorder the frame parameter first in GravityView and ConfigView
- curly brace goes on same line as class or struct declaration

This turned out to be a bigger change than I originally intended to make.

Gravity: Style fix, rename msg parameter to message

Gravity: Big code changes

* Reworked code style completely.
* Improved the behaviour of the particles.
* Made particles smaller (2,5x performance gain).
* Cleaned unnecessary includes.
* Tried improving performance with glCallList - performance dropped even more.
* Tried improving performance with glDrawArrays - no noticeable performance changes.

Gravity: Live update settings and cleanup

Now that this screensaver shows a preview, update the settings live
so that the display updates immediately.

Since this didn't work before this screensaver took a shortcut and only
updated the settings when the saver started.

Some other changes include:
* Update copyright header, add myself to the authors list.
* Convert Particle from using a BList to a BObjectList and remove casts.
* Use switch statement to set particle color that has a default case for blue.
* Initialize member variables to a default value in the constructor.
* Remove Constants.h, the remaining constants are in ConfigView.cpp
* Convert deprecated GroupLayoutBuilder to a LayoutBuilder template instance
* Convert GravitySource from a class to a struct since all members are public.
* Simplify realCount calculation to just a single left shift.
* A bunch of style fixes
- lots of whitespace fixes
- rename rect to frame in GravityView and ConfigView
- reorder the frame parameter first in GravityView and ConfigView
- curly brace goes on same line as class or struct declaration

This turned out to be a bigger change than I originally intended to make.

Gravity: Style fix, rename msg parameter to message

Gravity: Big code changes

* Reworked code style completely.
* Improved the behaviour of the particles.
* Made particles smaller (2,5x performance gain).
* Cleaned unnecessary includes.
* Tried improving performance with glCallList - performance dropped even more.
* Tried improving performance with glDrawArrays - no noticeable performance changes.