Fix bugs where hypertable-specific handlers were affecting normal Postgres tables.
Make it so that all TimescaleDB commands can run as a normal user rather than a superuser.
Updates to the code to make the extension compileable on Windows; future changes will add steps to properly build.
Move time_bucket functions out of public schema (put in schema where extension is).
Several other bugs fixes.

Notable commits * [1d73fb8] Fix bug with extension starting too early. * [fd390ec] Fix chunk index attribute mismatch and locking issue * [430ed8a] Fix bug with collected commands in index statement. * [614c2b7] Fix permissions bugs and run tests as normal user * [ce12104] Fix "ON CONFLICT ON CONSTRAINT" on plain PostgreSQL tables * [4c451e0] Fix rename and reindex bugs when objects are not relations * [c3ebc67] Fix permission problems with dropping hypertables and chunks * [040e815] Remove truncate and hypertable metadata triggers * [5c26328] Fix INSERT on hypertables using sub-selects with aggregates * [b57e2bf] Prepare C code for compiling on Windows * [a2bad2b] Fix constraint validation on regular tables * [fb5717f] Remove explicit schema for time_bucket * [04d01ce] Split DDL processing into start and end hooks

Thanks * @oldgreen for reporting time_bucket being incorrectly put in the public schema and pointing out permission problems * @qlandman for reporting a bug with INSERT using sub-selects with aggregates * @min-mwei for reporting a deadlock issue during INSERTs * @ryan-shaw for reporting a bug where the extension sometimes used pg_cache too soon