[FIX] web_editor: properly match snippet options' DOM

The snippet options are attached to `closest`, `all` and `is` functions
to be able to find/check DOM they are associated to. Their behavior
depend on the snippet option type: the search in the DOM is either done
in the body, the editable parts, the editable children only, ....

The problem is that when searching from a given DOM element, jQuery
won't match the elements whose selector contains this given DOM element.
Or in code terms, jQuery find function behavior is:
`$('A').find('A B')` <=> `$('A A B')` (not `$('A B')`)

This was indeed a problem on the job position apply form pages where the
main editable element is the <form/> element itself. Indeed, the snippet
options' selectors which began by 'form' were not able to match. Worse,
the selector is used for a jQuery search for drag & drop and saving but
not for initialization (where it is used as a `is` check on clicked
elements). So, some DOM were able to be modified by options but not
properly (re)configured before saving.

opw-705902
opw-741305