EZP-21346: eZOE: merged table cells are not saved in IE8

JIRA: https://jira.ez.no/browse/EZP-21346

# Description

Since the fix of [EZP-19401](https://jira.ez.no/browse/EZP-19401) in d801be0, merged cells are not correctly saved when IE8 is used. This is due to the fact that with this browser, the `colspan` attribute is actually called `colSpan` and our code did not take this into account.
This patch makes sure the `eZOEXMLInputParser` is able to handle the case variations on attribute names.

Note: there are several CS issues in `eZOEXMLInputParser::setAttributes` because most of the code comes from `eZXMLInputParser:setAttributes` and I want to keep trace of this.

# Tests

manual + unit tests