add OpenScienceMap protocol definition

src/org/oscim/database/oscimap/TileData.proto

@@ -0,0 +1,46 @@
+// Protocol Version 2
+
+package org.oscim.database.oscimap;
+
+//option java_package = "org.oscimap.database.pbmap";
+//option optimize_for = LITE_RUNTIME;
+
+//
+
+message Data {
+	message Element {
+		optional uint32 num_indices     = 1  [default = 1];
+		repeated uint32 tags            = 11 [packed = true];
+		// minimum is 1, number of coordinates for each geometry
+		repeated uint32 indices         = 12 [packed = true];
+		repeated sint32 coordinates     = 13 [packed = true];
+		optional uint32 layer           = 21;
+		
+		// building height, precision 1/100m
+		optional int32 height          = 31;
+		optional int32 min_height      = 32;
+		
+		// inteded for symbol and label placement, not used 
+		optional uint32 priority        = 41;
+		
+	}
+	// tags
+	required uint32 num_tags   = 1;
+	repeated uint32 keys       = 2 [packed = true];
+	repeated string values     = 3;
+	
+	// non-closed linestring	
+	repeated Element lines     = 11;
+
+	// polygons are implicitly closed 
+	repeated Element polygons  = 12;
+
+	// POIs
+	repeated Element points    = 13;
+
+	// prepared label placement, not used
+	repeated Element waylabel  = 21;
+
+	// tile is completely water, not used
+	optional uint32 water      = 31;
+}