fix issue #642 to add  druid pool support

add support preparedstatement execute batch

update less or equal symbol

udpate jdbcdriver maven repository

taosjdbc-driver have benn published to maven central repository, you can serach from https://search.maven.org or https://mvnrepository.com.

update english single quote and  =< to <=

release taos-jdbcdriver.jar to maven central repo

Fixed bugs relating to timestamps

- Fixed bug when the least significant bits of timestamp may cause time to be converted to 0
- Fixed small display bug with time and sig figs.

update english single quote and less than or equal to <=

taos-jdbcdrvier.jar has deployed to  maven central repo, you can search from https://search.maven.org or https://mvnrepository.com

Fixed bug where errors were printed as numbers instead of the string

# Conflicts:
#	src/util/src/ttimer.c

fix race in jni initialization