Merge branch 'develop' into master (cdcseacave#527)

Merge branch 'develop' into master (cdcseacave#512)

- open depth-map `DMAP` file format for easy utilization outside `OpenMVS` (see `ExportDepthDataRaw()` and `ImportDepthDataRaw()`)
- expose some depth-map functions in `SceneDensify.h`
- add global `ID` support to image structure to allow processing large scenes by splitting them into multiple sub-scenes to be processed individually

Merge branch 'develop' (cdcseacave#422)

* dense: improve PatchMatch algorithm

* viewer: improve pick-tool

* dense: increase patch size

* match: extend cylinder/cone functionality

* dense: visibility filter

* dense: adjust patch size for average scene types

* dense: correct normal

* common: log number of cores

* dense: various tweaks

* dense: clean-up

* cmake: improve CGAL linking

* dense: fix fuse with missing depth-maps

* cmake: fix find CGAL

* interface: import P camera list

* io: use legacy type names if requested

* interface: export dense point-cloud to COLMAP

* dense: improve refine stage

(cherry picked from commit d42ec8d4f04d69a2e41257bf391ccb29b1a147bb)

* dense: fine-tune patch-match

* common: fix VC2019 warnings

* common: fix build with opencv older than 3.4

* io: remove unused code

* dense: improve confidence computation

Merge branch 'develop'

Merge branch 'develop'