[Tizen][AT-SPI] Move AccessibilityAttributes to Accessible

[Tizen][AT-SPI] Move AccessibilityAttributes to Accessible

This patch allows setting arbitrary attributes on the Accessible level.
Previously this was only possible for Control, and thus application-side
customization of the attributes was unavailable for some other classes (most
notably Layer, which stands in for Window in the AT-SPI tree).

Change-Id: If6855d57faf05547d38460263b0a6184ba604339