Free variant 2.0.0

Release of both variants compatible with OpenCart 3.0.3.0 and 3.0.3.1 (see full review of changes since previous version)

Major

1. Add Google Shopping advertise extension (full variant)
2. Remove Citylink shipping extension (full variant)

Minor

1. Add Advertising extension extension (both variant)
2. Add Promotion extension extension (both variant)

Patch

1. Revise various module extensions (full variant)
2. Revise various OpenBay extensions (full variant)
3. Revise various payment extensions (both variant)