add custom latex option

Author: wanglongqi

writetex.inx

@@ -4,7 +4,6 @@
     <id>org.pecker.writetex</id>
 	<dependency type="executable" location="extensions">eqtexsvg.py</dependency>
 	<dependency type="executable" location="extensions">inkex.py</dependency>
-	<dependency type="executable" location="path">xelatex</dependency>
 	<param name="preamble" type="string" _gui-text="Preamble File: "></param>
 	<param name="read-as-line" type="boolean" _gui-text="Trade above as contents">false</param>
 	<param name="scale" type="float" precision="2" min="0.1" max="50" _gui-text="Scale Factor">1</param>
@@ -16,14 +15,18 @@
 		<page name="newfile" _gui-text="New from File">
 			<param name="inputfile" type="string" _gui-text="LateX Source File: "></param>
 		</page>
-		<page name="viewold" _gui-text="View OLD Text">
-			<_param name="old" type="description">Choose this tab if you would like to see the old TeX string.</_param>
+		<page name="viewold" _gui-text="View Original TeX">
+			<_param name="old" type="description">Choose this tab if you would like to obtain the original TeX string.</_param>
 		</page>
+        <page name="help" _gui-text="Help">
+            <_param name="help" type="description">You need at least one LaTeX command and one PDFtoSVG command to execute this plugin correctly. Please visit http://writetex.tk for more information. If you have any suggestion, feel free to open an issue in the repository.</_param>
+        </page>
 	</param>
 	<param name="pdftosvg" type="enum" _gui-text="PDF to SVG converter: ">
 		<_item value="1">PDF2SVG</_item>
 		<_item value="2">PStoEDIT</_item>
 	</param>
+    <param name="latexcmd" type="string" _gui-text="Latex Commnad used to Compile">xelatex</param>
     <effect>
                 <object-type>all</object-type>
     </effect>