ENYO-2288: Reflect reviewer's feedbacks on my patch
ENYO-2288: Reflect reviewer's feedbacks on my patch

Modified moonstone.design file.

Change:
- Changing accordion sub items' contents to starting with capitalizing.
- Changing the contents string to Button at the button component.
- moon.CheckboxItem(Group) --> moon.CheckboxItem (Grouped)

Note:
I added contextual popup component. Please review the part of them, too.
And I will add more components on this branch. If you feel difficulties, this style - one by one upload with pictures, please let me know.
I will commit whole code at once.

Test Result:
The pictures would be uploaded seperately on gitHub site.

Enyo-DCO-1.1-Signed-off-by: Sunggye <shiftpwr@gmail.com>

mcanthony/moonstone,mcanthony/moonstone,enyojs/moonstone,mcanthony/moonstone