GRASS GIS, in addition to importing data in its native formats via
`r.in.gdal`/`v.in.ogr` (and likewise `r.import`/v.import`),
also supports `r.external`/`v.external` which only link the data into
the GRASS DB.
Nevertheless, both `r.external` and `v.external` occasionally have problems,
especially on windows. E.g.:
- https://trac.osgeo.org/grass/ticket/3927
GRASS 7 Processing Plugin already has a setting that controls whether
`v.external` is used (disabled by default).
With this commit the complementary setting for `r.external` gets added too.
Usage of `r.external` is disabled by default. This is changing the existing
behavior, which was to use r`r.external`. The downsides of this change
should be the somewhat lower import speed + higher disk usage. Nevertheless
this way we have the same default value as `v.external` + we circumvent the
`r.import/v.import` shortcomings.
Since grass algorithms modify the parameters dictionary, we need to ensure
that they do this only a copy of the dict (and not a shallow copy). Otherwise
the parameter values included in the history log are the internally
modified values, not the original user-set ones
This is used in the algorithm's tooltip in the toolbox, and is intended
for single sentence description of the algorithm, e.g.
"Converts 2D features to 3D by sampling a DEM raster."
Convert grass algorithms to use short description for the
descriptive parts of their names, to cleanup the toolbox
and make it more uniform.
Since the underlying issues with the Python bindings are now fixed,
in most cases we can safely default to allowing an algorithm to
run in a background thread!!
So now we make this the default, and require individual algorithms
which are NOT thread safe to declare this. This includes algorithms
which directly manipulate the current project or layers (such as
setting layer styles), alter the selections in layers, or which
rely on 3rd party libraries (for now, SAGA and GRASS algorithms
are marked as not thread safe... TODO - someone more familiar with
these libraries can investigate and remove the flag if appropriate).
Also models are marked as non-thread safe. TODO: only flag an
individual model as thread-unsafe if any of its child algorithms
report this flag.
