Rename "submit" to "submit_btn"

Otherwise, wtforms use "submit" as id of the <input> tag, shadowing
javascript function ".submit()".

ogcp/forms/auth.py

@@ -23,6 +23,6 @@ class LoginForm(FlaskForm):
         label=_l('Password'),
         validators=[InputRequired()]
     )
-    submit = SubmitField(
+    submit_btn = SubmitField(
         label=_l('Login')
     )

ogcp/templates/auth/login.html

@@ -15,7 +15,7 @@
           {{ wtf.quick_form(form,
                             method='post',
                             form_type='basic',
-                            button_map={'submit':'primary'}) }}
+                            button_map={'submit_btn':'primary'}) }}
         </div>
         <!-- /.login-card-body -->
       </div>