[ZEPPELIN-1399] Refactor automatic interpreter name insert

[minahlee]

What is this PR for?

Refine automatic interpreter name insert. See below jira issue for detailed description

What type of PR is it?

Improvement | Refactoring

What is the Jira issue?

ZEPPELIN-1399

Screenshots (if appropriate)

• Do not insert interpreter name if previous interpreter name is not specified
  Before
  
  After
  
• Insert interpreter name of previous paragraph without running
  Before
  
  After
  

Questions:

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

[Leemoonsoo]

Tested and LGTM.
Thanks @minahlee for the great improvement.

[corneadoug]

@minahlee For the first case, it is actually the default interpreter.
For example, In Master when you create a new Note you will have '%spark' in the paragraph.
In this Branch, it will stay empty.

Another example would be using: sc.version in a paragrah without %spark

[minahlee]

@corneadoug actually I made it empty intentionally. please check out the discussion here

[corneadoug]

@minahlee Making a new line is a good improvement because some interpreters do not handle same line typing.

For removing the default interpreter, I don't have a strong opinion.
If we plan on having the backend provide the interpreter information in the paragraph and always show it outside of the text editor, we would remove this feature anyway.

However it could feel weird to have Release 0.6.1 have the default interpreter shown, 0.6.2 not showing it, then 0.6.3 or 0.7.0 have Interpreter always shown again but this time as part of the paragraph (not in text editor)

[minahlee]

I totally agree that we shouldn't make ux change often. But showing default interpreter in text is implemented only in master branch but not in previous release so I think it won't bring much of confusion.

[minahlee]

Reverted #1248 during the rebase since this PR already has implemented same functionality in this line.

[minahlee]

CI is green. Merge if there is no more discussuion