Change to use lxml instead of libxml2

[Semprini]

I've changed the uml2djlib.py to use the lxml library since compiling
libxml2 for windows 64 bit is a pain.

Here's the changes:

import lxml.etree

def generate_code(app_name):
xmi_file = '%s.xmi' % app_name
transform('uml2dj/xmi2djmodels.xsl', xmi_file, app_name+'/
_models.py')
transform('uml2dj/xmi2djmodels_generic.xsl', xmi_file, app_name+'/
models_generic.py')
transform('uml2dj/xmi2djadmin.xsl', xmi_file, app_name+'/
admin.py')
transform('uml2dj/xmi2djadmin_custom.xsl', xmi_file, app_name+'/
_admin_custom.py')
transform('uml2dj/xmi2djadmin_generic.xsl', xmi_file, app_name+'/
admin_generic.py')


def transform(stylesheet, source, target):
doc = lxml.etree.parse(source)
styledoc = lxml.etree.parse(stylesheet)

style = lxml.etree.XSLT(styledoc)
result = style.apply(doc)

f = open(target,"w")
f.write(style.tostring(result))
f.close()