Export commands deprecated

- Provided examplars of export commands re-implemented using the new
  _query command.
- Implemented export-xml.pl, export-xml.py, export-xml.rb.
- Implemented export-csv.pl.
- Implemented export-yaml.pl.
- Implemented export-ical.pl.

scripts/add-ons/export-xml.py

@@ -0,0 +1,62 @@
+#! /usr/bin/python
+################################################################################
+## taskwarrior - a command line task list manager.
+##
+## Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+## All rights reserved.
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 2 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+## FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, write to the
+##
+##     Free Software Foundation, Inc.,
+##     51 Franklin Street, Fifth Floor,
+##     Boston, MA
+##     02110-1301
+##     USA
+##
+################################################################################
+
+import sys
+import commands
+import json
+
+# Use the taskwarrior 1.9.4+ _query command to issue a query and return JSON
+command = "/usr/local/bin/task _query " + " ".join (sys.argv[1:])
+
+# Generate output.
+print "<tasks>"
+for task in commands.getoutput (command).split (",\n"):
+  data = json.loads (task)
+  print "  <task>"
+  for attribute in data.items ():
+    if attribute[0] == "annotations":
+      print "    <annotations>"
+      for anno in attribute[1]:
+        print "      <annotation>"
+        for item in anno.items ():
+          print "        <{0}>{1}</{0}>".format (item[0], item[1])
+        print "      </annotation>"
+      print "    </annotations>"
+    elif attribute[0] == "tags":
+      print "    <tags>"
+      for tag in attribute[1]:
+        print "      <tag>{0}</tag>".format (tag)
+      print "    </tags>"
+    else:
+      print "    <{0}>{1}</{0}>".format (attribute[0], attribute[1])
+  print "  </task>"
+print "</tasks>"
+sys.exit (0)
+
+################################################################################
+