Allow the user to opt out of inputting consumption tiers for household

[paulapreuss]

Either as an option or take the consumption tiers out all together. It has been decided to assume an average consumption level for all households as long as #121 / #13 won't be worked on, since the communities estimation (without conducting a survey or similar) is likely to be unreliable.

[paulapreuss]

• Upload average household consumption to online db (use household_avg.json and then delete / eventually fix demand_profiles fixture to include the generic demand profiles and household average)
• Exclude consumption tiers for household queryset if no community is selected
• Remove SHS threshold option if no community is selected (discuss if this should be removed altogether or replaced with a checkbox to exclude all households)
• (Fix SHS threshold selection if it breaks when adding another household timeseries)
• Figure out SHS graph display
• Compare results for CPs with consumption tiers vs. with average household consumption