feat(migration): add a migration script to warn about incompatibility of cwtags.

This is needed because a lot of people can waste a lot of time resolving
this issue: !208
in cwtags ; because of a monkeypatch.

see: cwtags!1
related: #367

--HG--
branch : 3.32

cubicweb/misc/migration/3.32.3_Any.py

+from pkg_resources import VersionConflict
+
+try:
+    from cwtags import __pkginfo__
+except ImportError:
+    pass
+else:
+    if __pkginfo__.numversion < (1, 2, 3):
+        raise VersionConflict(
+            "This version ({}) of cwtags is incompatible with CubicWeb >= 3.32. "
+            "Please, upgrade your version of cwtags to >= 1.2.3 before running "
+            "this migration.".format(__pkginfo__.version)
+        )