Adapt to the newest Table type, fix some previous adaptation issues

- Writers.Native is now adapted to the new Table type.

- Inline captions should now be conditionally wrapped in a Plain, not
  a Para block.

- The toLegacyTable function now lives in Writers.Shared.

test/command/4056.md

@@ -15,20 +15,27 @@ Blah & Foo & Bar \\
 \end{tabular}
 ^D
 [Table ("",[],[]) (Caption Nothing
- []) [(AlignLeft,Nothing),(AlignRight,Nothing),(AlignRight,Nothing)] 0
+ [])
+ [(AlignLeft,ColWidthDefault)
+ ,(AlignRight,ColWidthDefault)
+ ,(AlignRight,ColWidthDefault)]
+ (TableHead ("",[],[])
  [Row ("",[],[])
-  [Cell ("",[],[]) Nothing 1 1
+  [Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
    []
-  ,Cell ("",[],[]) Nothing 1 1
+  ,Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
    []
-  ,Cell ("",[],[]) Nothing 1 1
-   []]]
- [Row ("",[],[])
-  [Cell ("",[],[]) Nothing 1 1
-   [Plain [Str "Blah"]]
-  ,Cell ("",[],[]) Nothing 1 1
-   [Plain [Str "Foo"]]
-  ,Cell ("",[],[]) Nothing 1 1
-   [Plain [Str "Bar"]]]]
- []]
+  ,Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
+   []]])
+ [(TableBody ("",[],[]) (RowHeadColumns {getRowHeadColumns = 0})
+  []
+  [Row ("",[],[])
+   [Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
+    [Plain [Str "Blah"]]
+   ,Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
+    [Plain [Str "Foo"]]
+   ,Cell ("",[],[]) AlignDefault (RowSpan {getRowSpan = 1}) (ColSpan {getColSpan = 1})
+    [Plain [Str "Bar"]]]])]
+ (TableFoot ("",[],[])
+ [])]
 ```