plugin-api: deviced: Add attributes for display

plugin-api: deviced: Add attributes for display

New attribute:
 - id: DEVICED_DISPLAY_ATTR_LOCKSCREEN_BG_STATE
 - type: SYSCOMMON_RESMAN_DATA_TYPE_INT
 - setter: X
 - getter: O

New attribute:
 - id: DEVICED_DISPLAY_ATTR_INT_LCDOFF_REASON
 - type: SYSCOMMON_RESMAN_DATA_TYPE_INT
 - setter: O
 - getter: X

New attribute:
 - id: DEVICED_DISPLAY_ATTR_INT_STATE_TRANSITION
 - type: SYSCOMMON_RESMAN_DATA_TYPE_INT
 - setter: O
 - getter: X

The corresponding attributes may be changed during the
display state refactoring process.
These are necessary for plugin backend separation.

Change-Id: Iaaa53863e641e3bef401def4a0022aa14d055b96
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>