doc: vale fixups; clarifications clarify modal workflow, move bulk edit workflow from middle of edit item worflow to after. Clarify postfix expression use with Link items. Add rst() and markdown() to stext() and mark stext as depricated (maybe even this release cycle). More TAL examples. Refill some paragraphs to 65 character lines. Various other fixes pointed out by vale.

try:
    from html import escape as html_escape_  # python 3

    def html_escape(string, quote=False):
        # html_escape under python 3 sets quote to true by default
        # make it python 2 compatible
        return html_escape_(string, quote=quote)
except ImportError:
    # python 2 fallback
    from cgi import escape as html_escape  # noqa: F401