Added opera2drama XSLT transformation

templates/opera2drama.xslt

+<?xml version="1.0" encoding="utf-8" ?>
+<!--
+   This transformation converts TEI opera documents into standard TEI
+   drama documents. It's useful just in order to take advantage of
+   existing XSLTs for converting TEI drama to HTML.
+   -->
+<xsl:transform
+    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    xmlns:tei="http://www.tei-c.org/ns/1.0"
+    version="1.0">
+
+<xsl:output method="xml" />
+
+<xsl:template match="/">
+  <xsl:apply-templates />
+</xsl:template>
+
+<xsl:template match="musicalPrelude">
+  <xsl:apply-templates />
+</xsl:template>
+
+<xsl:template match="tei:sg">
+  <xsl:element name="sp">
+    <xsl:for-each select="@*">
+      <xsl:attribute name="{name()}"><xsl:value-of select="." /></xsl:attribute>
+    </xsl:for-each>
+    <xsl:apply-templates />
+  </xsl:element>
+</xsl:template>
+
+<xsl:template match="tei:singer">
+  <xsl:element name="speaker">
+    <xsl:for-each select="@*">
+      <xsl:attribute name="{name()}"><xsl:value-of select="." /></xsl:attribute>
+    </xsl:for-each>
+    <xsl:apply-templates />
+  </xsl:element>
+</xsl:template>
+
+<xsl:template match="tei:lyric">
+  <xsl:element name="l">
+    <xsl:for-each select="@*">
+      <xsl:attribute name="{name()}"><xsl:value-of select="." /></xsl:attribute>
+    </xsl:for-each>
+    <xsl:apply-templates />
+  </xsl:element>
+</xsl:template>
+
+<xsl:template match="tei:*" priority="-1">
+  <xsl:element name="{name()}">
+    <xsl:for-each select="@*">
+      <xsl:attribute name="{name()}"><xsl:value-of select="." /></xsl:attribute>
+    </xsl:for-each>
+    <xsl:apply-templates />
+  </xsl:element>
+</xsl:template>
+
+</xsl:transform>