Moved simulation controls *above* tabs
marketPeriods() needs +1 when still on the market

As the documentation correctly read, "including the current period":
i.e. it should be "1" for the first period the book is on the market.
Update belief 'x' for age > x, not >= x
Fixed book row dblclick; always refresh rdrs/bks.

Double-clicking was crashing because it was trying to load a
non-existant agent with the book id instead of a good.

Visualization redraw skipping when the visualization tab wasn't active
was breaking things with the new controls-above-the-tabs layout, since
you can now run/step from the readers or books tabs--but because the
visualization tab wasn't active, reader and book lists weren't being
updated.
Added full constructor; made default less variable

The previous non-informative model parameters were both highly
non-informative *and* highly variable; change the latter so that the
parameters are N(0,1) for the first K-1 parameters and N(1,1) for the
last one (instead of N(0, LARGE) for all of them.  n=1e-6 is preserved,
however, so that when using it as a prior it is still weak, but not as
variable.

Added a full model parameters constructor (which gets invoked by the
above constructor).