Adds implementation of SELECT_ALL action handling to PDE form editor
sections, in cases where it was missing.

TableSection or TreeSection subclasses now uses one common
implementation for selectAll, which is used by default in
#doGlobalAction (if not overriding by own custom version).

Change-Id: I50e547913e8bd4cdb53c0aeafc1ab9fc03d9a2ec
Signed-off-by: Martin Karpisek <martin.karpisek@gmail.com>