dashboard: tighten the printer, warranty and notification cards

PRINTER CARD is now supplies at or below 5 percent, a new
printers_dashboardpercent setting. The report and the card want different
scopes: the report lists anything the thresholds call low, which is right for
planning an order, while the dashboard is asking what to walk out and change
today - and a cartridge at 18 percent is not that. Lowest first.

PRINTER LOCATION WAS ALWAYS EMPTY. The lookup went through db.session.get on
locationid and produced nothing even where a location is set; the printers list
has always read it through the asset relationship, so the card does too now.

WARRANTY ROWS are identified the way the floor identifies them: the PC's
hostname and the MACHINE it drives, reusing the same lookup behind the warranty
page's machine column so the board and the report cannot disagree about which
bay a PC belongs to. No dates - expired or expiring is the whole decision when
scanning a board, and the exact day belongs on the report you order from.

NOTIFICATIONS are stacked: the type in full on one line, the message beneath,
trimmed to 100 characters with the rest on hover. Inline, the type was
truncated to make room for prose that was then truncated anyway, and neither
read. A tooltip is omitted when the text was not trimmed, because one repeating
what is already on screen is noise.

Two general additions: layout: 'stacked' on a card, and map.detailtooltip.

plugins/printers/plugin.py

@@ -286,6 +286,21 @@ class PrintersPlugin(BasePlugin):
 
         return [printerscli]
 
+    def get_settings_defaults(self) -> List[Dict]:
+        """Settings this plugin owns for the dashboard card."""
+        return [
+            {
+                'key': 'printers_dashboardpercent',
+                'value': '5',
+                'valuetype': 'integer',
+                'category': 'printers',
+                'description': 'Supply percentage at or below which a printer '
+                               'appears on the dashboard. Tighter than the '
+                               'low-supplies report, which is for planning an '
+                               'order rather than walking out to change one.',
+            },
+        ]
+
     def get_dashboard_widgets(self) -> List[Dict]:
         """Dashboard card: printers needing a cartridge.