Data usage strings, sweep touches, fixes.

Change strings around limiting background data.  Move limit/warning
sweeps above inspection sweeps, and teach about additional neighbors
on different axis.

Guard against DialogFragment.show(), fix pie chart to draw edges, and
remove data usage from battery UI.

Bug: 5341374, 5337650, 5337385, 5319465, 5236335
Change-Id: Iea8c2a2ab405b645d85abe34a0178d4b8874cdd5