fixes db crash; simplifies the ezic_db proxy module

The db crash happens when calling `ezic_db:get_all(X)` when `X` is not
a valid table name. `ezic_db_ets` crashes, causing the `ezic_db`
server to crash, tossing the database with it. The solution prevents
ezic_db_ets:get_all/1 from crashing, and instead returns an error
value.

The simplification here eliminated some code through
deduplication. The `handle_call` functions could be improved
similarly.

src/ezic_db_ets.erl

@@ -13,13 +13,17 @@
 	 , get_all/1
 	 , insert_all/1
 	 , wipe/1
+	 , implementation/0
 	]).
 
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % PUBLIC API
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 
+implementation() -> ?MODULE.
+
 zones(TzName) ->
     ets:select(zone, [{#zone{name=TzName, _='_'}, [], ['$_']}]).
 
@@ -43,7 +47,11 @@ flatzone(Date, TzName) ->
 
 
 get_all(Tab) ->
-    ets:lookup(Tab, Tab).
+    try ets:lookup(Tab, Tab) of X -> X
+    catch error:X -> {error, X}
+    end.
+	    
+	     
 
 
 insert_all(Records) ->