[ZEPPELIN-4389]. Add new interpreter if it is newly detected in interpreter folder

[zjffdu]

What is this PR for?

For now, if we put or build new interpreter for zeppelin in ZEPPELIN_HOME/interpreter folder, it won't be created automatically, user have to manually create new interpreter in interpreter page.

This PR is to create the newly detected interpreter automatically for user.

What type of PR is it?

[Improvement]

Todos

• - Task

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-4389

How should this be tested?

• Manually tested.
  Build a fresh new zeppelin without building shell interpreter, and then start it, no shell interpreter in the interpreter setting page. Then build a new shell interpreter and restart it, shell interpreter is displayed in the interpreter setting page.

Screenshots (if appropriate)

Questions:

• Does the licenses files need update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[zjffdu]

merge it if no more comments