Utils::BaseTreeView: Adjust column size by mouse click

Single click on either header or unoccupied part of the
view will toggle the respective column width between
a large value based on contents contents width and a
small fixed one (8ex). Previously it only expanded.

Change-Id: I2c5865a3b0bad7593a47976626d4c516e021c157
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
ProgressManager: Hide some internally used function from .h interface.

The indirection of the "virtual + implementation inheritance" pattern is
kind of subset of the "static" pattern, no need to have both.

Change-Id: I4e2c2742dae94819ee05c7925c02b954a8c6294b
Reviewed-by: Eike Ziller <eike.ziller@digia.com>