reledit refactoring
* js handling rewritten to exploit all form capabilities (such as file upload ...)
* attribute-like composite relations (one ttype, cardinality in '?1' from composite side) are more
cutely handled, with a 'add'/'delete' additional actions/icons
* a reledit_ctrl rtag to finely control: reloading, edition and default values
* a proper chapter in the documentation (book)
* many bugfixes
