ENYO-2794: Remove non-working Markdown Wiki anchors

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2794: balance `[` & `{` to appease README.md syntax checker

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2794: complete (add refs) & move PGB plugins usage description

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>