add CreatePlanet and put planet in solar system

models/solarsystem.go

@@ -0,0 +1,12 @@
+package models
+
+import "gopkg.in/mgo.v2/bson"
+
+const GALAXYSIZE = 50
+const SOLARSYSTEMSIZE = 15
+
+type SolarSystem struct {
+	Id       bson.ObjectId   `json:"id", bson:"_id, omitempty"`
+	Position int64           // position of the solar system in the galaxy, the maximum position is GALAXYSIZE-1
+	Planets  []bson.ObjectId // array with ids of the planets, if empty is equal to ""
+}