Launcher2: Increase size of overscoll box on home

(reworded from: Launcher: Press screen to slide, the blue box can't full-screen)

Slide HOME page to the left or right, Press screen to slide,
the blue box can not full-screen.

change some dimen values.

Change-Id: I875a7f4ce2e9dd1fb83935d94bac91f45c13c0da
CRs-Fixed: 421855