Pagination improvements

[JWCook]

Updates #276

• Exclude most pagination params from controller method signatures, in favor of using Paginator instead
• Update Paginator to support request positional args
• Fix ID-based pagination; total_results is only accurate for first page, since subsequent pages have decreasing total_results due to id_above param
• Move paginate_autocomplete() to places module, since that's the only place it's used
• Handle special pagination for get_observation_fields() within that function instead of trying to handle it generically in Paginator
• Remove paginate_all() support for V0 observations.json
• Update remaining API request functions to call paginate_all() instead of (harder to follow) @add_paginate_all decorator
• Move request estimating to separate Paginator.count() method instead of automagically doing it with total_results property