Summary of changes

(1) Support of master sheets in HSLF

org.apache.poi.hslf.model.MasterSheet  is a superclass of all master sheets -
Slide masters, Notes masters, Handout masters, etc.
For now HSLF supports only sLide masters, the implementation is in
org.apache.poi.hslf.model.SlideMaster.
Since it is a subclass of Sheet all required initializers added to SlideShow.

No more RichTextRun.getFontName(),  RichTextRun.getFontSize() and other style
accessors return null or -1! 
If style is not defined or the requested attribute is missing it is read from
the master sheet.

(2) support for color schemes.

If a RGB value is in the range [0x8000000, 0x8000007] it means that the color
from the sheet's color scheme is used. 

0x8000000 - use color with index 0
0x8000001 - use color with index 1
...
0x8000007 - use color with index 7
(ColorSchemeAtom holds 8 colors) 

This rule works for all type of colors: line, fill, font color, etc.

(3) Polished code for org.apache.poi.hslf.model.Shape and the subclasses. 

I had to change the signatures of the static constants in
org.apache.poi.hslf.model.Line.
I hate to do it but they were wrong and confusing. 

Yegor