[Serna] More convenient "Insert Symbol" dialogue

I would like to leave the "Insert Symbol" dialogue open most of the 
time, but it just gets in the way.  Result: it is constantly opened 
and closed.  What about a minimise/restore button on the title bar or 
perhaps turning it into a dockable palette?

It could do with some other improvements:

@ Add typographic spaces such as thin, mid, thick, en, and em quads 
as pale blue rectangles
@ Display the glyph name, either the PostScript name if there is one 
or the Unicode name when a glyph is clicked.  This would be 
especially helpful with typographic dashes, such as en dash, em dash, 
2-em dash, and hyphen.  In some fonts these are very similar in 
length and it becomes hard to distinguish them. Gentium appears to 
have two en rules and two em rules, for example (could be a font bug).
@ Show the Unicode number of a glyph when it is clicked.
@ Allow the user to re-order the glyphs in the Favorites grid.
@ Allow the user to insert the first ten Favorites glyphs by pressing 
Ctrl-0, etc. when the symbols dialogue has focus.
@ Allow the user to customise the dialogue so that particular 
sections can be grouped together conveniently.  At the moment, I use 
Latin A glyphs exclusively but have to scroll down way past Khmer 
Symbols to get to General Punctuation!  And it would be nice to also 
group Maths symbols with the other two.

Alternatively, allow the user to choose between the Serna symbol 
dialogue and the platform's supported glyph map, the Character Map in 
the case of Windows.  The Character Map in Windows implements a 
number of these ideas.