astrodatagui: add StarsDB.py

this class can only be instanciated once!

astrodatagui/db/StarsDB.py

@@ -0,0 +1,40 @@
+from enum import Enum
+import sqlite3
+
+class StarDBError(Enum):
+    NO_ERROR = 0
+    DB_CONNECTION_FAILED = 1
+    
+DB_NAME = "stars.db"
+
+class StarDB():
+    __instanceVar = None
+    
+    @staticmethod
+    def getInstance():
+        if(StarDB.__instanceVar == None):
+            return StarDB()
+        else:
+            return StarDB.__instanceVar
+        
+    def __init__(self):
+        if(StarDB.__instanceVar != None):
+            raise Exception("StarDB cannot be instantiated more than once!")
+        else:
+            StarDB.__instanceVar = self
+
+        self.error = StarDBError.NO_ERROR
+
+        try:
+            con = sqlite3.connect(DB_NAME)
+            self.dbCursor = con.cursor()
+        except:
+            self.error = StarDBError.DB_CONNECTION_FAILED
+            
+        if(self.error is not StarDBError.NO_ERROR):
+            raise Exception("StarDB cannot connect to the database!")
+        else:
+            self.initializeDB()
+
+    def initializeDB(self):
+        return