[FEATURE] Introduces mesh virtual datasets
With the mesh calculator the user can choose to create those "virtual" dataset groups that will be added to the layer. Then, for these dataset groups, values are not stored in memory but each dataset is calculated when needed whit the formula entered in the mesh calculator.
Those virtual dataset groups are saved with the project.
If needed, the user can remove them or can persist them on files to make them persistent.
Co-authored-by: Étienne Trimaille <gustrimaille@yahoo.fr>
[FEATURE] Introduces memory dataset groups for mesh layer. These dataset groups are temporary and are not kept when the project is closed.
Memory dataset groups can be created from the mesh calculator with a new option.
Allows the possibility to remove or save these memory dataset groups to a file with specified driver.
[MESH][FEATURE] Allow to select only specific subset of dataset groups in mesh layer tree
This could be done in the mesh layer properties dialog in the source tab.
A new tree view displays all the available dataset groups from the data provider. The dataset groups can be checked/unckecked and renamed.
This widget provides also buttons to load extra dataset group from files, to expand/collpase the tree, to check/unchek all items and to reset to default from the provider (for now, only the original name).
Then only the checked dataset group will be displayed in the active dataset widget in renderer settings.
