DTD Formatting implemented

[NikolasKomonen]

Fixes #221, #250, #268, #226

[fbricon]

With this PR, the DTD from #268 (comment) is broken after formatting.

it changes
<!ELEMENT dl (dt|dd)+>
into
<!ELEMENT dl (dt|dd) +>

The plus sign should stick to the closing parenthesis

[NikolasKomonen]

@fbricon Thanks, this was the one I forgot to finish.

[fbricon]

<!ATTLIST img
  src     CDATA  #REQUIRED
  alt     CDATA  #IMPLIED
  height  CDATA  #IMPLIED
  width   CDATA  #IMPLIED
  align   CDATA  #IMPLIED
  border  CDATA  #IMPLIED
  hspace  CDATA  #IMPLIED
  vspace  CDATA  #IMPLIED
  %all;>


<!-- Hypertext anchors.
	CONSTRAINT: A elements are not allowed inside
	other A elements, a fact that XML cannot express. -->

is turned into

<!ATTLIST img
   src CDATA #REQUIRED
   alt CDATA #IMPLIED
   height CDATA #IMPLIED
   width CDATA #IMPLIED
   align CDATA #IMPLIED
   border CDATA #IMPLIED
   hspace CDATA #IMPLIED
   vspace CDATA #IMPLIED
   %all;

<!-- Hypertext anchors.
	CONSTRAINT: A elements are not allowed inside
	other A elements, a fact that XML cannot express. -->

the closing bracket disappears. Also, there's an extra space added in front of each attribute.

[NikolasKomonen]

@fbricon Updated

[NikolasKomonen]

@fbricon tested again with dtds, all looks good.