use "building:part" in object descriptions

[mkoniecz]

What steps will reproduce the problem?

1. create multipolygon with entire building
2. create multipolygon with building:part
3. notice labelling differences

What is the expected result?

building:part multipolygin has useful name

What happens instead?

only building multipolygon has useful name

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

​https://www.openstreetmap.org/way/155905486

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-10-01 23:59:36 +0200 (Mon, 01 Oct 2018)
Build-Date:2018-10-01 22:08:47
Revision:14289
Relative:URL: ^/trunk

Identification: JOSM/1.5 (14289 en) Linux Ubuntu 16.04.5 LTS
Memory Usage: 502 MB / 869 MB (109 MB allocated, but free)
Java version: 1.8.0_181-b13, 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 (34535)
+ buildings_tools (34572)
+ continuosDownload (82)
+ imagery_offset_db (34641)
+ measurement (34529)
+ reverter (34552)
+ todo (30306)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.

[mkoniecz]

Ideally first multipolygon would have name "building:part" and second "building=hotel"