improve service manager

- do not start sea server automatically
- replace _SERVICE in FRAPPY_HISTORY by service name
- imporve error messages
- no fiddling around with sys,path, reply on PYTHONPATH for
  finding packages

frappyman.py

@@ -39,6 +39,13 @@ class FrappyManager(ServiceManager):
       <instance> is one of %s
     """
 
+    def prepare_start(self, ins, service):
+        start_dir, env = super().prepare_start(ins, service)
+        his = env.get('FRAPPY_HISTORY')
+        if his:
+            env['FRAPPY_HISTORY'] = his.replace('_SERVICE', '_' + service)
+        return start_dir, env
+
     def do_gui(self, ins='', service='main'):
         try:
             self.check_running(ins, service)