Add handling for context loss and regain behaviour

Add handling for context loss and regain behaviour

[Problem] Dali doesn't handle context loss
[Cause] Never tested.
[Solution]

Fixed ReplaceSurface handling for window surface case. Fixed window destructor to ensure
indicator is correctly removed.

Added new application policy for dealing with context loss. If the application
doesn't support context loss, then Dali must instead retain resource data or have
some means to re-load it.

Added a new data retention policy to PlatformAbstraction. This allows Core to query
what to do with bitmap data and mesh data on context loss / resume.

Change-Id: Ic98d04ada6915eaa600490c1e9465232b3ed6b64
Signed-off-by: David Steele <david.steele@partner.samsung.com>