[ZEPPELIN-4504]. Fix searching of keywords in notebooks

[zjffdu]

What is this PR for?

This PR improve the lucene search via storing the index in filesystem by default. So that even after zeppelin restart, we can still recover the index. This PR introduce several new configurations:

• zeppelin.search.index.path. --> folder path for storing lucene index
• zeppelin.search.use.disk --> whether use disk as index storage.
• zeppelin.search.index.rebuild --> whether rebuild index when zeppelin start

What type of PR is it?

[Bug Fix]

Todos

• - Task

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-4504

How should this be tested?

• CI pass

Screenshots (if appropriate)

Questions:

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