Add initial UsageUploadService implementation

This service grabs the statistics from the SciJava UsageService, filters
it for relevant objects -- specifically, those from official update
sites -- transforms the filtered result into a JSON string, and then
uploads it to the ImageJ usage server at http://usage.imagej.net/.
fixup! Add initial UsageUploadService implementation
fixup! fixup! Add initial UsageUploadService implementation
fixup! fixup! fixup! Add initial UsageUploadService implementation