[7.0] l10n_ch_sepa - payment to partner with & in name

[Yannick Vaucher @ Camptocamp]

Trying to generate a payment order with & in the name of a partner will crash :

../l10n_ch/l10n_ch_sepa/base_sepa/msg_sepa.py",
line 63, in _is_xsd_valid
parser=parser)
File "lxml.etree.pyx", line 2957, in lxml.etree.parse
(src/lxml/lxml.etree.c:56230)
File "parser.pxi", line 1550, in lxml.etree._parseDocument
(src/lxml/lxml.etree.c:82492)
File "parser.pxi", line 1578, in lxml.etree._parseMemoryDocument
(src/lxml/lxml.etree.c:82774)
File "parser.pxi", line 1457, in lxml.etree._parseDoc
(src/lxml/lxml.etree.c:81572)
File "parser.pxi", line 965, in lxml.etree._BaseParser._parseDoc
(src/lxml/lxml.etree.c:78242)
File "parser.pxi", line 569, in
lxml.etree._ParserContext._handleParseResultDoc
(src/lxml/lxml.etree.c:74498)
File "parser.pxi", line 650, in lxml.etree._handleParseResult
(src/lxml/lxml.etree.c:75389)
File "parser.pxi", line 590, in lxml.etree._raiseParseError
(src/lxml/lxml.etree.c:74722)
XMLSyntaxError: xmlParseEntityRef: no name, line 134, column 25

Mako entities need to be filtered.

Patch will be attached in a MP