This adds support for the Multidatastream entity type, as
implemented in the SensorThings version 1.1 "MultiDatastream extension"
While the specification mandates that MultiDatastreams have an
optional polygon geometry, I've encountered numerous servers
which expose different geometry types for this entity or which
return errors when attempting to read the geometries from
MultiDatastreams. Accordingly we always expose an option to
load MultiDatastreams as geometryless layers alongside the
default option to load them as polygon layers, to handle a
wider range of connections.
This mode can be used when each band in the raster layer is associated
with a fixed time range, eg. NetCDF files.
The user can either manually populate a table with begin/end dates for
each band in the raster, or build the table using QGIS expressions
which return datetime values.
In this mode, the user can specify a QGIS expression for the
lower and upper value corresponding to raster bands, using
variables like @band, @band_name and @band_description.
E.g
@band * 100
Can be used when each band represents a 100 m vertical slice
of data.
The expression will be evaluated when required to determine
the actual elevation range corresponding to each band.
This differs from the existing "Fixed Elevation Range Per Band"
mode in that "Fixed Elevation Range Per Band" requires users
to manually enter an elevation for each band separately,
and these values are then treated as constants. That mode works
best for rasters with non-regular steps in the band
elevation values, while this new mode is better for regular
band elevation steps
In this mode, each band in the raster can have a fixed elevation
range associated with it. This is designed for data sources which
expose elevation related data in bands, eg netcdf files, such
as a raster with temperate data at different ocean depths.
This introduces a new option for specifying how raster layers
have associated elevation. It permits a fixed elevation range
to be set for the layer. It can be used when the layer has
a single fixed elevation, or a range (slice) of elevation values.
Users can set the lower and upper elevation range for the layer,
and whether the lower or upper limits are inclusive or
exclusive.
When enabled, the layer will only be visible in elevation
filtered 2d maps when the layer's range is included in the map's
z range.
These flags reflect that retrieval of the provider's 2D or 3D extent
retrieval via QgsDataProvider::extent()/extent3D() are ALWAYS guaranteed
to be trivial/fast to calculate and involve absolutely no extra work.
This mode is purely for animated map movies -- the user can set
the total number of frames, and the animation will progress
frame by frame for that number of frames, advancing the current
map settings frame at each step (also the @frame_number expression
variable).
No time based filtering of data is performed when in this mode.
starting PyQGIS
We can't use `None` as a keyword exposed to python, it's reserved.
Also move the enum to Qgis before making it part of public stable
API.
