Trend page is not refresh friendly

[eidekrist]

Copied from #143:

Scenario 2:

Setup

• Run cse-server-go (start it again), load house demo, press play

Action:

• While running, have one of the trends page open. Press refresh

Result:

• Models don't disappear (ok)
• Trend freezes (not ok)
• A lot of data is dumped to the terminal (not ok)

The client sends which plot is active as the first command after refresh, but does not have enough data to know what the actual id of the plot is, only the index. A possible solution could be to use the plot id as route parameter instead of index.