provide autofix for removal of unneded boundary=administrative tags

[mkoniecz]

What steps will reproduce the problem?

1. create boundary=administrative relation
2. add unneded boundary=administrative tags on boundary ways
3. run validator

What is the expected result?

Validator offers to remove unneeded boundary=administrative from all outer ways of boundary=administrative relation as it is violation of "one feature one OSM element" rule and pointless duplication.

In case where admin_level is present on ways - it should also be removed.

What happens instead?

Validator generates "boundary=administrative without admin_level: warnings.

Please provide any additional information below. Attach a screenshot if possible.

Note that rendering in JOSM amkes clear that tags on boundary relation, without tags boundary ways is completely sufficient.

​https://www.openstreetmap.org/way/197110173 - example boundary
​https://www.openstreetmap.org/relation/6941793 - one of relations using it

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-02-23 17:46:51 +0100 (Sat, 23 Feb 2019)
Build-Date:2019-02-24 02:30:49
Revision:14802
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14802 en) Linux Ubuntu 16.04.5 LTS
Memory Usage: 641 MB / 869 MB (293 MB allocated, but free)
Java version: 1.8.0_201-b09, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: :0.0 1920x1080
Maximum Screen Size: 1920x1080
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (34867)
+ buildings_tools (34867)
+ continuosDownload (82)
+ imagery_offset_db (34867)
+ measurement (34867)
+ reverter (34867)
+ todo (30306)

Last errors/warnings:
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: java.net.SocketTimeoutException: Read timed out
- W: Unable to delete archived backup file <josm.userdata>/autosave/deleted_layers/Data Layer 9_20190224_203113089.osm