ref: one codebase for hover tooltip and freezed tooltip

- rename variables for URL template, use templateSrv to render URL links
- fix visibility of tooltip items and url template help popup whe the light theme is used
- rework Tooltip settings pane, organize tooltip editor fields
- rename properties in panel config, implement migration logic for legacy configuration
- close button for the frozen tooltip
- use relative positioning for proper page scrolling

dist/plugin.json

@@ -17,7 +17,6 @@
     "links": [
       {"name": "Github", "url": "https://github.com/flant/grafana-statusmap"},
       {"name": "MIT Licence", "url": "https://github.com/flant/grafana-statusmap/blob/master/LICENSE"}
-
     ],
     "screenshots": [
       {"name": "Panel with light theme", "path": "img/flant-statusmap-panel.png"},