Fix improper cast of <row_count> from int64 (on some systems) to int32
Merge pull request #13 from ChannelMeter/null-values-fix

Fix improper cast of <row_count> from int64 (on some systems) to int32
acu81679 - add support for map<text, text> collection type
acu81679 - add support to handle map<text, text> binding in the stmt prepare&exec.
acu81679 - wording correction + clearer expression