Retain original value in TimestampValue

[eolivelli]

Currently we only keep a reference to a parsed java.sql.Timestamp, but java.sql.Timestamp.valueOf uses local machine Timezone to parse the timestamp value, this is not good for statement rewriting if jSQLParser is running on a separate machine (like a server) with different JVM configuration

[coveralls]

Coverage increased (+0.007%) to 86.614% when pulling 39af0ec on eolivelli:fix/keep-raw-timestamp into 3f51651 on JSQLParser:master.

[eolivelli]

Thanks for accepting my patch.
At HerdDB we hope can can see current master released soon 👍

[wumpz]

I will try it, however, I have no much time at the moment.

[eolivelli]

Thank you much!