Use confidence to fix whitelist

With this the most obvious problem is fixed. However there
are two remaining items : we should still enforce whitelist
when there are no close candidates at all, and we should
start in confident mode when pressing the globe key.

Bug: 18063142
Bug: 18130489
Bug: 18132240
Bug: 18136721
Bug: 18200415
Change-Id: Ibc0571ae35fc28f8d13760aa86b25db1163d3e31