elc_multibuttonentry: role of MBE item, MBE updated, and state_set_get API added.

elc_multibuttonentry: role of MBE item, MBE updated, and state_set_get API added.

Summary:
Reason for role change:
MBE items do not  act like push buttons, they need to maintain their status and at a time only one item can be selected, they act like radio buttons.
Role change of MBE from entry to panel, because MBE is just a container and entry is one of the children, when entry gets access frame, it will work as how entry works, but making MBE role as entry does not work as expected and also MBE should not receive highlight as a whole but only its children should receive highlight one more reason why MBE role cannot be entry.
state_set_get API added to get items state.

Test Plan:
When atspi mode is enabled the access frame has to
navigate directly on item and not on MBE as a whole and state has to
be read out

Reviewers: kimcinoo, cedric

Reviewed By: cedric

Subscribers: cedric, govi, rajeshps, jpeg

Differential Revision: https://phab.enlightenment.org/D4925

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>