table: modify quoting in JDBC CREATE TABLE statements.

Previously, all table and column identifiers were indiscriminately
quoted when generating CREATE TABLE and similar SQL statements when
performing JDBC operations on a database.  It turns out that,
especially in the presence of mixed-case identifiers, this is not
harmless (SQL92 quoting does not work like shell quoting).
Markus Demleitner drew my attention to this, following trouble
with PostreSQL interaction with STIL.  After several rounds of
working out what might work best, I now try to rename any words
which might possibly be problematic, and quote column names.

It seems very difficult to get this working in a way that will work
robustly for most or all RDBMSs.  Further experimentation/iteration
may be required.
ttools: improve aesthetics and efficiency of line plotter.

The line plotter now uses a new class LineTracer to draw dot-to-dot
lines between multiple points.  LineTracer aggregates points and
performs a small number of drawPolyLine calls rather than lots of
drawLine calls.  This gets dashing right (doesn't start a new dash
at each point) and performs various efficiency improvements.
It can also be reused elsewhere.
The old version got dashing wrong becau
topcat: fix issue with line dash selector.

Some funny problem to do with the fact that a null and DashComboBox.SOLID
are used to mean the same thing.  Problem reported by Aaron Robotham.
Couldn't reproduce it, so not certain if this is the fix, but slightly
improved behaviour for me in any case.