Support for extra functions required by BI tools

[rupal-bq]

Using Docker image amazon/opendistro-for-elasticsearch:1.1.0
Dataset: Flights sample data (loaded through Kibana)
SQL Plugin version: 1.1.0.1
Tableau version: 2019.3

Tableau generated SQL (MySQL dialect): SELECT POWER(`kibana_sample_data_flights`.`dayOfWeek`, 2) AS `sum_Calculation_160722252357632000_ok`\nFROM `kibana_sample_data_flights`\nGROUP BY 1.1000000000000001

Generated SQL without quotes (#212) and Group By (#215): SELECT power(dayOfWeek, 2) AS sum_Calculation_160722252357632000_ok FROM kibana_sample_data_flights

Result: No data

{[\n]"
  "error": {[\n]"
    "reason": "There was internal problem at backend",[\n]"
    "details": "The following method is not supported in Schema: power",[\n]"
    "type": "UnsupportedOperationException"[\n]"
  },[\n]"
  "status": 500[\n]"
}

Expected Behaviour: Should return square of all values present in column dayOfWeek.

List of functions which have similar issue:
Number functions

• ATAN2
• COT
• SIGN
• POWER

String functions

• ASCII
• RTRIM
• LTRIM
• LOCATE
• LENGTH
• REPLACE
• LEFT
• RIGHT

Logical functions

• IFNULL
• ISNULL

[dai-chen]

I think this is the limitation in our JDBC formatter. Currently the formatter doesn't recognize many SQL function and map it to correct result type in JDBC spec.

[dai-chen]

For these functions, first we need to change grammar to pass both new and old SQL parser. Then based on their behaviors in standard SQL or MySQL, we need to figure out what's the right DSL to generate.

[dai-chen]

Another function list that we need to support: #235.

[chloe-zh]

@dai-chen I will do #235 along with this issue.

[chloe-zh]

PRs will be separated and submitted respectively according to the function/operator type.