Variety of small style / UX tweaks from Vibha.

Increase font size of edit text.

Make article background white not super light gray.

Make edit text background super light gray.

Switched eye icon to right arrow.

Updated colors of edit summary panel and items.

Edit summary panel drag handle improved - turns to (taller)
down arrow when dragged. down arrow tap hides panel.

Added padding to right of nav bar labels so long i18n
text doesn't cram right up to left edge of right nav buttons.

Edit summary panel now docks more cleanly with bottom of nav
bar.

Keyboard hidden if other edit summary panel items tapped.

Use right arrow instead of eye icon for edit preview action
button.

Change-Id: I649738c22c048d8e15c1740f580eb83a699968e7