Trigger task metadata refresh from web

[tcouch]

Although task metadata such as number of observations, number of uploads, and bounding box should be updated every time someone uploads data, it might be useful to enable the web portal to trigger a refresh via an API call. So as long as we can pass a task ID to the api, it should be able to look at every object under that task ID project, calculate the metadata, and update it in the dynamodb table.