gaia: start adding TAP support.

Note considerable changes to RegistryResults_vot3.xsl, this now creates an
output row per capability, not Resource, as each capability represents an
endpoint of sorts.
gaiavo: add VOTable 1.3 xsd

Copied from Mark Taylor's votable package
gaiavo: make 1.3 xsd compatible with other xsd definitions
gaiavo: fix BINARY support to work with variable unicode columns and when we have just a single column in BINARY
gaiavo: add VOTable 1.3 support classes
gaiavo: implement VOTable 1.3 support, including BINARY2
gaiavo: add generic RegTAP ADQL generator utility class
gaia: extend astrocat open command to test if catalogue is already open
gaiavo: add support for RegTAP queries

Lots of associated refactorings as knowledge of response contents are moved into specialised classes
gaiavo: don't test URLs for RFC 3986 compliance

as a consumer it's better to work with what's given
gaiavo: fixes to the various older services to work with new registry type
gaia: add script to query TAP service about useful things
gaiavo: add controls and visualisation of TAP tables and related metadata
Merge branch 'tapdevel'

First GAIA TAP developments.