ttools: document ADQL geometry reserved words addition

Add notes to the stilts and topcat user documents relating to the
previous commit.
ttools: update examples for optional RA/Dec parameters

A recent change (4555a51) made it optional to specify ra and dec
parameters for certain tasks (coneskymatch, sqlskymatch, pixfoot).
Update the examples in the user document to show some examples of
invoking these commands with absent ra/dec parameters.
vo: generalise VOTable serialization in TapQuery uploads

Allow the caller to specify how uploaded tables are serialised into
VOTables, by supplying a VOTableWriter instance, rather than hardcoding
a specific one (was BINARY, VOTable 1.2).  Note this does change one of
the TapQuery constructors in a backwardly-incompatible way.

Using this, add some additional tests to the taplint upload stage,
trying uploads with both TABLEDATA and BINARY options.
vo: make TAP load window jobs window slightly less annoying

The "Running Jobs" window previously scrolled the Job Details panel
to the bottom of the scroll pane every time a new job was selected
or the job details were refreshed.  It did this in a jerky way.
I've stopped the jerkiness and made it scroll to the top instead,
which is an improvement, but I don't know how to stop it changing
the scroll position at all.

Also moved the field for Job URL display outside the scroll pane
so it never gets scrolled out of view.