Remove zope.interface dependency
Use regular unittest

No change in API, no bug fix

- (Comments and PI as sibling)
- New nodes stay orphan.

by a modification. This patch address this issue.

with a unique identifier.

 * /erp5/object[@id='foo']/title
 * /erp5/object[@gid='2130123']/title

* Add tests

prefix in builded xpath expression.
* Update test according to this modification

this avoid reading entirely the files if they differ during reading.
- Use parser with remove_blank_text flag to normalise output and c14n.
- Do not append tail to xupdate elements if not needed.

- Support xupdate:insert-before element
- Order attributes updates