search and send a request to join team, unified message variable values in the custom_msg file

Done
===
```
- search and send a request to join team ( WaitList )
- unified message variable values in the custom_msg file are applied to views of all apps
```
To do
===
```
- Accept wait member to join the team
- Team page 
- Unified variable values in one file
```

As The number of Our test code files is over 200,
Unified variables(module, object, ...) have been needed. 
In custom_msg.py, our repetitive messages are contained.
These message variables are applied to views of all apps.

Later, models(name, email, password, ...) in test case will be applied
in a file.