CommonUri added.

Contains two functions: getFilename + getUrl.
CommonUri: @param comment updated
Changelog improvement added
CommonUri: decoding htmlspecialchars
CommonUri: remove special characters by their normal character
CommonUri: return added
CommonUri: reserved characters (RFC 3986) comment updated
CommonUri: '|' needs to be replaced
CommonUri: removed redundant space, etc...
SpoonFilter::urlise replaced by CommonUri::getUrl
CommonUri: RFC comment changed
Merge pull request #1 from siesqo/CommonUri

I merged it in master, but there are still some problems to be solved.
https://github.com/forkcms/forkcms/pull/349