Excerpt-Include macro does not create backlinks on migration

[acotiuga]

The problem is caused by the fact that the excerpt-include macro in Confluence uses the default-parameter parameter to store the reference which actually means there is no parameter name, and this is how it looks to have a parameter without name but with value: {excerpt-include:My page name|nopanel=true}.

Steps to reproduce:

1. Create a new page in Confluence with excerpt macro.
2. Create a new page in Confluence with excerpt-include macro, including the excerpt from the previous page.
3. Export the space and migrate it to XWiki

Actual result:
The XWiki page with the excerpt macro does not have a backlink to the XWiki page with the excerpt-include macro.
Expected result:
The XWiki page with the excerpt macro has a backlink to the XWiki page with the excerpt-include macro.

[acotiuga]

Hi @michitux, @raphj! Here's a new PR for this issue: #214. Thanks for reviewing it!