Add the start of the class.

Add initial conditions.
Add begin functions.
Add ways to set bus and others.
Add structure to class design.
Modify some of the enums to better describe purpose.

Author: SFE-Brudnerd

library.properties

@@ -7,3 +7,4 @@ paragraph=
 category=Other
 url=https://github.com/sparkfun/SparkFun_AS7331_Arduino_Library
 architectures=*
+depends=SparkFun Toolkit