Fetch all parameters at once

• Set David Robinson as maintainer
• Turn slashes into hyphens when saving a connection cache file (supports tiered access, in which parameters can contain "/")
• Changed get_creds to get all parameters from AWS in one query

Extra arguments to dbConnect

• Offer redshift as an alternative, using the Postgres driver
• DBI is now in DEPENDS rather than IMPORTS
• Allow passing ... to create_connection (and create_connection_pool) to pass additional parameters to dbConnect (or to dbPool).

Basic caching

More context in #3. This will speed up repeatedly making connections, which will be useful for dashboards that are calculated on the fly.

Both pools and connections can be made

Getting connection params from aws takes time. Either local credential files need updating after key rotation or dashboards need a global connection pool. This release adds a function that spits out a pool.