Crs parameters in algorithm settings in modeler
This makes it easier to pick static CRSes for the parameter,
and also makes it obvious to users that they can use a fixed
CRS parameter in their model (as opposed to one taken from
a layer or input)
This adds a new input type for expression inputs. Expression
inputs can be linked to a parent layer so that the builder
shows the correct fields and layer variables.
It's designed for two use cases:
1. to be used when an algorithm specifically requires an expression,
eg Select by Expression and Extract by Expression.
2. to be potentially used as a replacement input instead of string
or number literals in algorithms. Eg - if the simplify algorithm
tolerance parameter was replaced with an expression paremeter, then
this expression would be evaluated for every feature before
simplifying that feature. It would allow parameters to be calculated
per feature, as opposed to the current approach of calculating
a parameter once before running the algorithm. It would also
mean algorithms like "variable distance buffer" would no longer
be needed, as a single "buffer" algorithm could then be used
for either a fixed distance, field based, or expression based
distance.
accept numeric, file and table field inputs in modeler
This allows a non-string parameter to be reused as a string
parameter in contexts where it makes sense.
This commit restores some pre 3.0 processing behaviour for number inputs.
Now, if a number input is required outside of modeller than a spin box
will be shown instead of a free text input.
Clicking the expression builder button results in an expression
which is evaluated immediately to avoid users expecting that
the expression will be evaluated per feature.
Tags are used while searching in the toolbox. This should help with
finding algorithms when the exact name is not known, eg
you could search for "envelope" or "bounds" and find the
'Polygon from Layer Extent' algorithm.
At the moment it's quite hard to discover algorithms which exist
when you don't know what their called and have to instead search
for every possible naming variant which could exist...
Eg, allows you to search "line merge" and find the "Merge lines"
algorithm. Should make it easier for users who don't know the
exact name to find algorithms.
