change to native Dialogs if possible
Merge pull request #253 from burgerdev/master

Fix for bug #252
enabled tracking workflow autodiscovery; improved ImportError handling in workflows init
more protection against missing tracking dependency
incorporate 5d threshold operator into synapseObjectWorkflow
add a colortable to output layer
returned small filtered components as colored
make objects layer visible by default
shell: Removed "Play Recording" menu item.  Must use command-line to play recordings.
object feature selection.

* new feature selection dialog.

* features implemented in plugins.

* new dependency, yapsy, for plugin management.
Fix issue #227
clean up carving applet
work on path input of ilastik.py
save selected object features
Changed order in which applets are created and connected in IlastikShell in order to fix Issue #229. It should be fixed now.
remove brush size names, #256.

Still todo: adjust "Size:" string in GUI to read "Brush size:"
use new signature of notify_failed
belonging to commit on Issue #229 and work on the ilastikShell
carving: implement navigation to position of maxmimum uncertainty
OpEnsembleMargin: Copy roi before modifying it.