add river/surfspot customization features

[titaniumbones]

• create a dashboard that tracks levels. Display should show level in blocky letters that use the same color-coding for good/bad/shoulder as used in graphs, and also display a blocky up, down, or "stable" arrow. On mouseover it might be nice to list the last five or 6 readings to give a sense of how rapid the change is. User should opt in to track these values -- choose some favourite streams, probably
• Allow user to choose streams to check -- should be a form listing all known spots. Only these will be displayed in menus
• Allow user to modify level ratings -- maybe you disagree with my assessment? Can still use the system but change the values.
• Add stream definitions to DB -- stop storing in static json, instead fetch from DB initially,then modify using user settings described above
• Allow user to add new streams -- these will be maybe vetted somehow via email or GH issue? -- but in the meantime can use as personalizations, see above.