Allow including hidden map layers to map links

[ernoma]

Currently, when I create a map link from the Oskari UI (Oskari v. 1.56) only the visible map layers will be included in the link even if I have opened map layers but hidden them. However, it would be useful to let user to choose whether to include the hidden maps to the link or not.

The maps that have 100% transparency are included in the link but it maybe a bit confusing.

The issue has been commented on the old oskari-docs repository: oskariorg/oskari-docs#233

[ernoma]

I did not remember this issue though... So, not high priority