Bhv 10842 brookepeterson v2

(This is continuing working on https://github.com/enyojs/moonstone/pull/1403. )
1. Remove unnecessary DOM nodes, simplify the classes attached to the arrows
2. Refract code so it is more concise and easy to read
Cause/Appoaches
1. The SimpleIntegerPicker.js used enyo.Button kind for the "moon-simple-integer-picker-button", which is not necessary. Those arrows could be just a generic control, no need to use enyo.button which cause issues in non-latin font because classes clash.
2. No need to add moon-icon class (which will result unneeded css rules),
3. For overlay: those two dive
<div class="moon-scroll-picker-overlay-left"> </div>
<div class="moon-scroll-picker-overlay-left-border"> </div>
Those two can be combine to generate the desired dark shadow (remove one DOM)
4. In the SimpleIntegerPickerSample.js, 
This line caused the three inline-block times to switch direction. For the picker switching left-button-container and right-button-container is not need, regardless LTR or RTL , the arrow stay the same, only the picker client item direction need to be set.
inSender.parent.applyStyle("direction", active ? "rtl" : "ltr");
With this in mind, we can remove all the RTL css in the less file
Fix:
1 Deleted a bunch of unnecessary class.
2. For RTL using float: right (or maybe text-align: right), anyway the layout issue should be considered by App developer.