ENYO-544: Don't call stabilize() on every setScroll[X|Y]

In the fix for ENYO-483, we introduced a call to stabilize()
every time setScrollX() or setScrollY() was called. This seemed
like a logical place to clamp the scroll position and eliminated
the need for some manual calls to stabilize() elsewhere, but it
turns out that some existing behavior in moon.ScrollStrategy
depends on allowing the position to be temporarily out of bounds.

The Moonstone behavior is complicated, but seems to be reasonable,
so reverting this particular change (affecting ScrollMath,
TouchScrollStrategy and TranslateScrollStrategy). The corresponding
change is also being made in moon.ScrollStrategy.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)
ENYO-549: VerticalGridDelegate doesn't trigger scroller remeasure

Issue:

enyo.VerticalDelgate (in its adjustBuffer() method) triggers the
list's scroller to measure its bounds after list pages have been
generated / regenerated. However, enyo.VerticalDelegate overrides
adjustBuffer() without calling the super method, so this
measurement doesn't occur.

Under some circumstances, this doesn't matter, since scroller
measurement is also triggered by other events (e.g. wheel
scrolling, starting a drag, etc.) – but it is problematic in other
cases (where there's a persistent, manipulatable scroll controller
like a draggable thumb; or when the list generates pages in the
middle of a long animated scroll).

Fix:

To fix, we'll just add the trigger to VerticalGridDelegate as well.

HorizontalDelegate.adjustBuffer() does call the super method, so no
need to add it explicitly in that case.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)
Merge pull request #940 from enyojs/ENYO-544-graynorton

ENYO-544: Don't call stabilize() on every setScroll[X|Y]

Reviewed-By: Cole Davis (cole.davis@lge.com) 
Integrated-By: Cole Davis (cole.davis@lge.com)
Merge pull request #941 from enyojs/ENYO-549-graynorton

ENYO-549: VerticalGridDelegate doesn't trigger scroller remeasure

Reviewed-By: Blake Stephens (blake.stephens@lge.com)
Integrated-By: Aaron Tam (aaron.tam@lge.com)
Update version string to 2.5.2-rc.1