[422686] Fix a report issue.

The makeWrittable method must enable the text widget.
[422478] Migrate VSM and representations file from Viewpoint to Sirius

This commit adds new migration participants:
* One which maps nsURIs of all the Sirius EPackage with their current
value.
* Another which replaces type of Diagram (notation.Diagram#type: Sirius
replaces Viewpoint)

In doing so, the IMigrationParticipant contract is revised so that
a participant can provide an EPackage instance from a nsURI.

The version in the file (odesign or aird) does not corresponds to a
Sirius version but more to a file format version (7.0 file format
corresponds to Sirius 0.9)
The nsURI target strings have been hardcoded because this migration must works even with Sirius 2.0 in which the nsURI field on the EPackage implementation may have changed by then.

Change-Id: I00b48f346688eafc9773a8f7484d645ece2acaea
[422478] Change conversion action to remove old Viewpoint nature.

This commit updates the conversion action (ModelingToggleNatureAction:
menu "Configure/Convert to Modeling Project" on an old Viewpoint
Modeling project) to remove the old Viewpoint nature if it exists.
So Viewpoint users must launch this action on their existing modeling
projects after  switching to Sirius.

Change-Id: I6492a839c7bd6b6bb2dd6e20fbb04a7b85f2df3a
Signed-off-by: Laurent Redor <laurent.redor@obeo.fr>
[422638] Remove obsolete references to EditionTableExtensionDescription

Change-Id: I187400eea579a7dac8ffe7dae2300975b4cb3616
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>