Create proper entity attribute id for uploaded layer with > 1 layer in map

[jackgrossman18]

Describe the bug
When the user attempts to add a new area entity to an uploaded layer, currently, the new osmEntity will be given a negative id. This conflicts with the id of an existing node with the layer that was uploaded.

This is related to a open hoot-ui PR

To Reproduce
Upload two layers to the map then add a new entity feature ( add area ). The node will be placed at the desired location and the location of n-1_(mapId) on the map.

Resolving

Expected behavior
The given node id for the area feature that's being added should take the current index of that layer into consideration, then continue from whatever that number may be.

[jackgrossman18]

@brianhatchl @mattjdnv