Add visual dividers to more suggestions panel

java/res/drawable-hdpi/more_suggestions_divider.png

java/res/drawable-hdpi/suggestions_strip_divider.png

java/res/drawable-mdpi/more_suggestions_divider.png

java/res/drawable-mdpi/suggestions_strip_divider.png

java/res/drawable-xhdpi/more_suggestions_divider.png

java/res/drawable-xhdpi/suggestions_strip_divider.png

java/res/layout/suggestion_divider.xml

java/src/com/android/inputmethod/keyboard/Key.java

java/src/com/android/inputmethod/latin/MoreSuggestions.java