Create the "read full entry" link independently of the blog post syntax

The bug BLOG-98 pointed to the problem that the "Read the full entry" link in the blog overview page is created in wiki syntax and only valid for xwiki/1.0 or xwiki/2.x. As a workaround the link has been omitted from the other syntaxes.

Instead of omitting the link or try to create it in the right way for all possible syntaxes it should be possible to create the link as XDOM representation and append it to the parsed blog post excerpt in a way independent of the wiki-syntax of the blog post.

This will need some changes to the velocity macros in Blog.BlogCode - the macro getEntryContent should not return the content as string but as XDOM, or the "read full entry" needs to be appended in displayEntryContent instead.