Use new BlueMapAPI features

[TBlueF]

...and add server-network compatibility.

Changes in this PR:

• Moved to image-storage for Server-Network compatibility
• marker-icons get smaller on zoom-out
• Fixed icon-alpha appearing as black
• Appended (offline) to the POI-Marker's description (not the label)

I made these changes just to test new BlueMap features and provide them as is, only rudimentarily tested :) Use them as you wish ^^

[TBlueF]

This PR is done, i'll un-draft it as soon as the used API-Version is actually released ^^