This commit is the result of the squashing of rfc4_dev branch in a single
commit. It implements mostly RFC 4 related work.
* Grid handling:
- remove obsolete and presumably unfinished implementation of grid catalog functionality
- all grid functionality is in grids.cpp/.hpp
- vertical and horizontal grid shift: rework to no longer load whole grid into memory
- remove hgrids and vgrids member from PJ structure, and store them in hgridshift/vgridshift/deformation structures
- build systems: add optional libtiff dependency. Must be explicitly disabled if not desired
- add support for horizontal and vertical grids in GeoTIFF, if libtiff is available
- add GenericShiftGridSet and GenericShiftGrid classes, relying on TIFF grids, that can be used for generic purpose grid-based adjustment
- add a +proj=xyzgridshift method to perform geocentric translation by grid. Used for French NTF to RGF93 transformation using gr3df97a.tif grid
- deformation: add support for +grids= for GeoTIFF grids
- horizontal grid shift: fix failures on points slightly outside a subgrid (fixes #209)
* File management:
- add a filemanager.cpp/.hpp to deal with file related work
- test for legacy proj_api.h fileapi
- proj.h: add proj_context_set_fileapi() and proj_context_set_sqlite3_vfs_name() (fixes #866)
- add capability to read resource files from the user writable directory
* Network access:
- build systems: add optional curl dependency
- add a curl-based default implementation for network related functionality
- proj.h: add C API to control network functionality, and optionaly provide network callbacks
- add data/proj.ini with default settings
- add a SQLite3 local cache of downloaded chunks
- add proj_is_download_needed() and proj_download_file()
* Use Win32 Unicode APIs and expect all strings to be UTF-8 (fixes #1765)
For backward compatibility, if PROJ_LIB content is found to be not UTF-8 or
pointing to a non existing directory, then an attempt at interpretating it
in the ANSI page encoding is done.
proj_context_set_search_paths() now assumes strings to be in UTF-8, and
functions returning paths will also return values in UTF-8.