Add ClickHouse support

[filipecaixeta]

ClickHouse is an OLAP database with some additional syntax

Were is an example of a query that uses most of the additional syntax

CREATE TABLE arrays_test
(
    s String,
    arr Array(UInt8)
) 
ENGINE = MergeTree() 
ORDER BY s 
PARTITION BY tuple();

INSERT INTO arrays_test VALUES ('Hello', [1,2]), ('World', [3,4,5]), ('Goodbye', []);

SELECT s, arr
FROM arrays_test
ARRAY JOIN arr
PREWHERE s='Hello'
WHERE arr>1
LIMIT 1 BY s
LIMIT 10
FORMAT Pretty;

Result
s    |arr|
-----|---|
Hello|  2|

query="SELECT s, arr FROM arrays_test ARRAY JOIN arr PREWHERE s='Hello' WHERE arr>1 LIMIT 1 BY s LIMIT 10 FORMAT Pretty;"
print(sqlparse.format(query, reindent=True, keyword_case='upper'))

SELECT s,
       arr
FROM arrays_test
ARRAY JOIN arr
PREWHERE s='Hello'
WHERE arr>1
LIMIT 1 BY s
LIMIT 10
FORMAT Pretty;

Please refuse the pull request if you think it is a very specific database

[codecov[bot]]

Codecov Report

Merging #619 (8bb07ce) into master (23d2993) will decrease coverage by 0.80%. The diff coverage is 40.90%.

@@            Coverage Diff             @@
##           master     #619      +/-   ##
==========================================
- Coverage   96.82%   96.02%   -0.81%     
==========================================
  Files          20       20              
  Lines        1514     1536      +22     
==========================================
+ Hits         1466     1475       +9     
- Misses         48       61      +13     

Impacted Files	Coverage Δ
sqlparse/filters/aligned_indent.py	100.00% <ø> (ø)
sqlparse/filters/reindent.py	95.00% <14.28%> (-3.27%)	:arrow_down:
sqlparse/engine/grouping.py	97.45% <36.36%> (-2.55%)	:arrow_down:
sqlparse/keywords.py	100.00% <100.00%> (ø)
sqlparse/sql.py	97.62% <100.00%> (+0.02%)	:arrow_up:

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[ne1r0n]

Good initiative @filipecaixeta. Please, consider adding other specific types of join, i.e. ALL, ANY, ASOF, SEMI.