[#6541] Added import_id for GC tracker importer

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Refactored import_id and ImportIdConverter

Made default import_id implementation use a dict to
record source and other info for use with multiple importers.

Requires Ming 0.3.9 (from 0.3.x branch) for MIM bug fixes for
tests to pass.

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Added AuditLog on GC tracker import

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Added audit log on project import

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Added import_id and AuditLog to Trac ticket importer

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Added import_id and AuditLog to GC repo importer

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Revert to exact match on import_id and fix ImportIdConverter docstring

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] Override url in AuditLog on tool import

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6541] bump trac & GC wiki importers, for their audit log addition
[#6640] expose votes_up and votes_down in ticket API & export
Merge branch 'db/6640' of https://git-wip-us.apache.org/repos/asf/incubator-allura into db/6640