added postgresql plugin

[breadval]

Hi.
I added postgresql plugin.
I checked with jpetstore demo project and it work properly except binding values with sql query string.

Thanks.

[nstopkimsk]

Thank you for your contribution.
Pinpoint v1.5.0 will be released next week. so we are going to merge your pr after that.

[breadval]

Hi, congratulations on version 1.5.0 release.
I updated version from 1.5.0 to 1.5.1.
Thanks.

[emeroad]

Thank you for your contribution.