Provide intuitive way to run dynamic select form

• Until 0.6.0
  Zeppelin run instantly on select option change.
  ZEPPELIN-1013 There is an issue that when there are multiple select forms in one paragraph, user should wait the code to be run every time select option is changed.

• 0.7.0
  ZEPPELIN-2000 Made paragraph to be run on enter key event after selection, but this can confuse long time Zeppelin user who is used to previous version behavior.

There are some suggestion to handle this issue:
https://github.com/apache/zeppelin/pull/1974#issuecomment-277502448
https://github.com/apache/zeppelin/pull/1974#issuecomment-277502684