Adds Random Notes (#5644)

Adds SSDocs, which manages randomly spawned documents.
    These documents can be specified in a json file or in a database.
    Adds /obj/random/document and adds /obj/random/document to the loot pool of /obj/random/loot.

Actually adding the notes to spawn is up to loredevs. If there are no notes to choose from, /obj/random/document will leave a blank sheet.

The notes can have HTML in them, meaning custom CSS and images. We're giving the loredevs a good bit of responsibility here.

code/_helpers/text.dm

@@ -449,6 +449,7 @@ proc/TextPreview(var/string,var/len=40)
 	t = replacetext(t, "\[time\]", "[worldtime2text()]")
 	t = replacetext(t, "\[date\]", "[worlddate2text()]")
 	t = replacetext(t, "\[editorbr\]", "<BR>")
+	t = replacetext(t, @"[image id=([\w]*?\.[\w]*?)]", "<img style=\"display:block;width:90%;\" src = [config.docs_image_host]$1></img>")
 	return t
 
 /proc/html2pencode(t)