Alessandro Pasotti 497a7da9de Added API methods to retrieve only valid maplayers
... and to count them

Tests updated accordingly, note that from now on
the assumption that a layer store or a layer project
contains only valid layers will not be true anymore.

To be honest it has never been true, because a
layer can become invalid at any time during
its life cycle, so better never assume that a
layer from the store or from the project is vaid.
2018-11-05 10:24:35 +01:00
..
2018-10-14 22:13:58 +02:00
2018-10-24 11:13:54 +02:00
2018-10-16 12:52:48 +02:00
2018-11-04 19:22:09 +10:00