Memory data provider should not be saved

[ccrook]

Layers built with the memory data provider should not be saved to the project file, as when the file is reloaded, the data for the layers is no longer available. This means that reloading the project does not restore it to its saved state.

I think that when Quantum saves a project then it should check for in memory layers, and provide the option of saving them to a persistent provider, or removing them from the project.

Also it would good when an in memory layer is saved to a shapefile (or other persistent provider) from the legend right click menu if the layer was replaced with the saved layer. This make it much easier to make in memory layers persistent in the project. At the moment I think you need to save the layer, then load the saved version, and then remove the in memory layer.