add colNames and colNameIndicies to ResultSequence

- same as in ResultSet
detect nullable types and call nullify in toStruct
Merge pull request #36 from MartinNowak/columnNames

add colNames and colNameIndicies to ResultSequence
Merge pull request #37 from MartinNowak/nullify

detect nullable types and call nullify in toStruct
fix empty for ResultSequence

- Range wouldn't stop correctly when all rows were fetched
Merge pull request #38 from MartinNowak/SequenceEmpty

fix empty for ResultSequence
Merge remote-tracking branch 'upstream/master'