Escaping, table layout, and document fixes

Quoted Klammertext specials (^@ ^| ^# ^^ ^: ^*) and ^'...'^ regions now
survive re-processing (held as escape markers until final output);
:after_apply phase functions receive and return raw target text.

Tables: :hpos element position (center|left|right|<length>) replaces the
unimplemented :center/:indent; the ranged cell override is renamed
:justify; :column_width works in html (colgroup widths) and gains
'fill' -- the remaining width, capped at the column's widest entry, in
both targets; a table wider than the text column warns on the console;
table edges without an outer line set their text flush on the margins.

@document: no empty title bar for untitled documents; @vfill fills to
the bottom of the window in html (pure CSS); @vspace in plain text;
new @dot klammer; monospace email links.

sks/target/target.k

@@ -44,7 +44,7 @@ The LaTeX transformations supported by the SKS are:
 @@@
 
 @@@target tex | LaTeX
-:escape \ \textbackslash{} & \& { \{ } \} $ \$ % \% _ \_
+:escape \ \textbackslash{} & \& { \{ } \} $ \$ % \% _ \_ ^# \^# ^^ \textasciicircum{}
 @@@
 
 @@@target pdf | PDF from LaTeX