topcat: fix some documentation issues

Adjust the main montage screenshot slightly so that the plot toolbar icons
are the new ones not the old ones.  This montage still needs a major
overhaul since currently none of the plots shown use the new plotting
windows.

Also fix up the section on missing transparent/translucent shading modes -
these two were conflated in the docs, now there is one section for each.
topcat: repaint shading mode selector on mode change

The shading mode panel was not getting repainted properly when the
mode changed from Transparent to Translucent, though for most other
changes a revalidate caused a repaint as a side effect.  Now repaint
explicitly.
ttools: add "duff query" test to taplint

The TAP validator query tests now include a query with intentionally
illegal syntax, to check that the error document is returned in the
correct way.
vo: fix line-end bugs in UwsJob

The code for posting multi-part messages in UwsJob, and used by TapQuery
for doing TAP table uploads, was placing line ends incorrectly
(see Goldfarb's First Law of Text Processing).  In particular,
an uploaded VOTable lacked a CRLF before the terminating multipart boundary.
This was reported by Michael Tibbets at CFA, and was causing
incorrect error reports in taplint's UPL (upload) stage.
Fixed.

While I was there, I spotted another lurking bug related to multipart
line ends which would have caused errors if more than one stream
param header had ever been used (though I don't think it ever had) -
fixed that too.
ttools: avoid taplint E-MDQ-CTYP error report for BOOLEAN!=boolean

This behaviour may technically be an error since BOOLEAN TAPType doesn't
exist, but it's better reported elsewhere (if at all).
vo: add new TapQuery constructor

TapQuery now has a different constructors for upload and non-upload queries;
only the former can throw an IOException.  This simplifies invocation for
cases where upload is not required.
table: note SQL correspondences in JoinType documentation

1and2 = INNER, 1or2 = FULL OUTER, all1 = LEFT OUTER, all2 = RIGHT OUTER.
I've only just learned enough SQL to get this right.