For morden osm server, Tile level has been extended to 20 from 18.

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1.declare multi tile layers in ini file:
[tiles]
name0=OSM
name1=google
name2=bing

2.set tile server addresses, Image Alpha Channel in UI

for a.tile.openstreetmap.org\b.tile.openstreetmap.org
c.tile.openstreetmap.org
using Y % 3 == 0,1,2 ->a,b,c

2. add OCX interface to set local cache path and tile expire value.
Signed-off-by: goldenhawking <goldenhawking@163.com>