improved error messages

Change-Id: I5fc24b1e53a4343b29dbd5dddea27324dac17ee6
Implemented TextGraphics for manipulating BitmapText with method
chaining.
Updated sample code.

Change-Id: I040a8e6282fb2896d44d4910994ebf4e933ed97a
Implemented PointGraphics with method chaining, not used yet.

Change-Id: I393103a716af36a0fd83d94c42709ccd9ff368f7