[patch] add checks for duplicate relations, same relations and same ways to validator

[bilbo]

This patch adds three checks to validator:

Same ways: similar to duplicate ways (ways having same nodes), but regardless of tags. Severity warning.

It is quite common in some places to find duplicated ways, but with one of the copies having slightly different tags (like one being residential, one having name, while the second not, etc ...). There is no automatic fix, user have to solve this manually (although usually the proper fix is just to delete one of the ways).

Duplicate relations: 2 or more relations having exactly same tags and exactly same members in exactly same order and same roles - these duplicates usually come from botched import uploads. Severity error.
Automatic fix is to delete all relations except the one with lowest ID (similarly like it is done with duplicated ways)

Same relations: same as above, but with severity warning and checking only members and their roles, not tags. And no automatic fix for this one (though in the map usually these duplicates differ in relatively uninteresting tags like source, etc ...).

[bilbo]

Patch to add checks for duplicated/same relations and same ways