Offer-motivated features: :hline defaults, ranged :hpos, @date :days, :bottom none

- @table: a writer's :hline/:vline replaces the default lines; new
  boundary name 'none' removes all lines
- @table: ranged :hpos argument overrides :cell_hpos per cell
  (\multicolumn{1} in tex; positions a colspan anchor's merged cell)
- @date/@datetime: :days offset argument (sks/date/date.py)
- @document: ":bottom none" suppresses the footer (\pagestyle{empty})

Also carries the escape-system generator/renderer fixes, per-cell-range
:format, and uppercase .TTF/.OTF font recognition from klammertext-dev.

sks/table/table_cell.py

@@ -12,10 +12,13 @@ class Cell:
     def __init__(self, text, font, hpos,
                  top, right, bottom, left,
                  left_all, right_all,
-                 rowspan, colspan, first_column=False):
+                 rowspan, colspan, first_column=False, hpos_forced=False):
         self.text = text
         self.font = font
         self.hpos = hpos
+        # An :hpos override on an ordinary cell must reach the tex target
+        # through a \multicolumn{1} (the column spec sets the default).
+        self.hpos_forced = hpos_forced
         self.border = border.Border(top, right, bottom, left, left_all, right_all)
         self.rowspan = rowspan
         self.colspan = colspan
@@ -74,7 +77,7 @@ class Cell:
             left_marker = "xL" if remove_left else "L" if self.border.left_all else ""
             right_marker = "Rx" if remove_right else "R" if self.border.right_all else ""
             result = f"{left_marker} {result} {right_marker}"
-        if remove_left or remove_right:
+        if remove_left or remove_right or self.hpos_forced:
             pos = self.hpos
             if self.border.left_all and self.border.left:
                 pos = "|" + pos