### What is this PR for?
Add new interpreter to Python group: `%python.sql` for SQL over DataFrame support
### What type of PR is it?
Improvement
### TODOs
* [x] add new interpreter `%python.sql`
* [x] add test
* [x] make Python-dependant tests, excluded from CI
* PythonInterpreterWithPythonInstalledTest
* PythonPandasSqlInterpreterTest
* run manually by `mvn -Dpython.test.exclude='' test -pl python -am`
* [x] add docs `%python.sql`
* [x] make `%python.sql` fail gracefully in case there is no Pandas or PandaSQL installed
* [x] after #747 is merged - rebase and remove `-Dpython.test.exclude=''` from both profiles
### What is the Jira issue?
[ZEPPELIN-1115](https://issues.apache.org/jira/browse/ZEPPELIN-1115)
### How should this be tested?
`mvn -Dpython.test.exclude='' test -pl python -am` should pass or manually run
- Given the DataFrame i.e
```
%python
import pandas as pd
rates = pd.read_csv("bank.csv", sep=";")
```
- SQL query it like
```
%python.sql
SELECT * FROM rates LIMIT 10
```
### Screenshots (if appropriate)
### Questions:
* Does the licenses files need update? No, no dependencies were included in source or binary release
* Is there breaking changes for older versions? No
* Does this needs documentation? Yes
Author: Alexander Bezzubov <bzz@apache.org>
Closes#1164 from bzz/ZEPPELIN-1115/python/add-sql-for-dataframes and squashes the following commits:
0f2f852 [Alexander Bezzubov] Fail SQL gracefully if no python dependencies installed
aca2bdf [Alexander Bezzubov] Fix typos in docs ⚡158ba6a [Alexander Bezzubov] Remove third-party dependant test from CI
5fe46fc [Alexander Bezzubov] Update Python Matplotlib notebook example
72884c8 [Alexander Bezzubov] Add docs for %python.sql feature
e931dc4 [Alexander Bezzubov] Make test for PythonPandasSqlInterpreter usable
76bbb44 [Alexander Bezzubov] Complete implementation of the PythonPandasSqlInterpreter
f6ca1eb [Alexander Bezzubov] Add %python.sql to interpreter menue
11ba490 [Alexander Bezzubov] Add draft implementation of %python.sql for DataFrames
