[UWS,TAP] Fix timestamp format. Now, each returned date will expressed in UTC and using the ISO8601 format. Any given date is also expected in UTC (or with a time zone offset) and in ISO8601Format. These rules apply also for uploaded tables and for timestamp columns in a query result.

[TAP,ADQL] Improve and remake a part of the database connection. Missing javadoc has been added when missing in the modified tables.

[TAP] Improve TableIterator + Adapt ResultSetTableIterator (particularly because of the last commit about TAPType and VotType) + Add a TableIterator for VOTable input: VOTableIterator + Add its JUnit test case

[TAP] Add the interface TableIterator (whose implementations let iterate over any kind of table data set) and its first implementation for ResultSet + JUnit test case