Updating Python Image registration examples to be more robust for
input types and show methods
Use tr1::function pointers for active members

removed most of the command updater for the active measurement
variable, replacing it with function pointers.

Change-Id: If6edc5da3072da463296cd611143708e68eff770
catch ITK's abort exception, and handle

catch other ITK exceptions in the execute method and adapt to a
SimpleITK exception

Change-Id: Iebe2c298b1bc8a2930b1e0f35140165861b142df
Tweak Event Watcher to get process object

Change-Id: Idec825c26b9783b1174005b82f42ae66f0435483
adding a progress example

Change-Id: I04d0dbd1afcb5d23fc743af87aef4d191133e2da
making more methods in Process Object virtual

Change-Id: Ic3b2a6b6563e2c3f83361dd82e734c8c9ddf8313
Chaning ProcessObject::AddCommand to take command as reference

Change-Id: Ib445bbbf1e1b970e9dc57d73d2cb2f143a89a2f8