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/phases.py

@@ -304,17 +304,28 @@ def make_pdf_from_tex(filename, K, twice=True):
         os.system('rm -rf {}/{}.{}'.format(dirname, basename, unused_ext))
 
 
+# Emitted by @vspace.txt (sks/block/block.k), one marker per line of space.
+# An @eval result consisting only of whitespace is trimmed away by the
+# Klammermachine, so vertical space must travel as markers and become
+# newlines here, after blank-line runs have been normalized.
+vspace_marker = "__VSPACE__"
+
 def justify_blocks(text, K=None):
-    rgx = re.compile("\n\n+", re.S)
     delim = '__DIVIDE__'
-    text = rgx.sub(delim, text)
+    text = re.sub("\n\n+", delim, text)
     result = ""
     for par in text.split(delim):
-        #print(par)
-        if par[0] not in {' ', '['}:
+        stripped = par.strip()
+        n = stripped.count(vspace_marker)
+        if n and stripped == vspace_marker * n:
+            # A paragraph of only @vspace markers: n blank lines in addition
+            # to the normal paragraph separation.
+            result += "\n" * n
+            continue
+        if par and par[0] not in {' ', '['}:
             par = "\n".join(textwrap.wrap(par, width=80))
         result += par + "\n\n"
-    return result
+    return result.replace(vspace_marker, "\n")