Added a stylable transition to styling example.

Added a stylable transition to styling example.

Added Enable / Disable transitions to ImageChannelControl which
can be set via the style sheet.

Added a Visibility attribute to ImageChannelControl which
forces the enable / disable transition to be executed when
the visibility changes.

Added 3 different transitions to the style sheet:
1) a cross fade
2) a longer cross fade
3) a scale change.

Change-Id: I82a1f0e4e4c89ae0bdcb1c59ce01a0a918f17afd
Signed-off-by: David Steele <david.steele@samsung.com>