Add development option to force everything resizable

Add a development setting to force all activites to be
resizable. Currently, a restart is required after changing
this setting. Also remove all the code that forced a single
task to be resizable, as we have a global option now.

Bug: 24815256
Change-Id: I3237c9b6ce96ff9aa9819592ab0c2807fde88dc4
4 files changed