Add necessary packages to requirements.txt

This does not include `pycairo`, as it does not provide an egg and therefore can't be installed via pip.
We should consider `cairocffi` instead, but `pycha` (last update 2013) would have to be patched then.

server/requirements.txt

@@ -1,3 +1,4 @@
+django
 ujson
 xml_marshaller
 six
@@ -12,3 +13,9 @@ python-ldap
 MySQL-python
 reportlab
 bitarray
+python-dateutil
+defusedxml
+requests
+xenapi
+geraldo
+pycha