Implemented numerical support for ContentValues.getAsBoolean()

Copied existing Android functionality for getAsBoolean for Number values. Zero is false and anything else is true. Added unit tests to back this up as well as for String and Boolean values.
Merge branch 'getAsBoolean_withNumbers' of git://github.com/jferlisi/robolectric into jferlisi-getAsBoolean_withNumbers

* 'getAsBoolean_withNumbers' of git://github.com/jferlisi/robolectric:
  Implemented numerical support for ContentValues.getAsBoolean()

Conflicts:
	src/main/java/org/robolectric/shadows/ShadowContentValues.java
	src/test/java/org/robolectric/shadows/ContentValuesTest.java