Date expressions

[ChrissW-R1]

Added ANSI SQL scalar functions CURRENT_TIMESTAMP, CURRENT_TIME and CURRENT_DATE

[coveralls]

Coverage decreased (-0.2%) to 83.346% when pulling 8e985b6 on conterra:date-expressions into 3bc316d on JSQLParser:master.

[wumpz]

Please sqash all connected commits to one. Make a pull request for each change (means issue). You know although github does state your PR as mergable, I still want to check the changes.

Why should something like CURRENT_TIMESTAMP be a keyword? This could be easily handeled as a normal identifier or column name. This would be the more general approach too, since CURRENT_TIMESTAMP is a very SQLServer specific one. So each time an oracle user defines a column CURRENT_TIMESTAMP he will get it as a function.

[coveralls]

Coverage increased (+0.03%) to 83.594% when pulling b272c45 on conterra:date-expressions into 3bc316d on JSQLParser:master.

[ChrissW-R1]

As you can see in http://users.atw.hu/sqlnut/sqlnut2-chp-4-sect-4.html#sqlnut2-CHP-4-SECT-4.1 not only the MS SQL Server supports this scalar functions.
We make this changes, because these functions were returned as column names!

[wumpz]

As I said (column names), were is the problem? Saying that I at the moment learned that CURRENT_TIMESTAMP is ANSI Sql. So provide a single squashed commit pr for exactly this issue and I will merge it.

[coveralls]

Coverage increased (+0.03%) to 83.596% when pulling 6feb782 on conterra:date-expressions into 3bc316d on JSQLParser:master.

[ChrissW-R1]

New pull request: #280