wrap V4 background layers in 3D OLCS by using v4 background store

[mki-c2c]

• [x] use raster fallback layer for 3d in OLCS
• [x] handle layer exclusion => https://jira.camptocamp.com/browse/GSLUX-644
• [ ] register styles correctly for raster layers in 3d => https://jira.camptocamp.com/browse/GSLUX-648
• [x] handle 3D layers in catalog -> https://jira.camptocamp.com/browse/GSLUX-642
• [x] chase all occurences of this.backgroundLayerMgr_ = ngeoBackgroundLayerMgr => https://jira.camptocamp.com/browse/GSLUX-645
• [ ] retrieve style reset button => https://jira.camptocamp.com/browse/GSLUX-646
• [ ] fix permalink => https://jira.camptocamp.com/browse/GSLUX-647
• [ ] sync medium style editor with style store => https://jira.camptocamp.com/browse/GSLUX-647

[mki-c2c]

hello @tkohr you are right, we should just remove the dead code. Just remove the lines which you highlighted, and those after the return statements. I was kind of afraid, but I see no need to keep them. We can always come back in git history if needed.

[tkohr]

Ok, I just commented the dead code for now to keep it until 3D is completely done.

The v4 dependency now points on latest commit, so I think we are ready to merge.