fixed union types
Adds pattern matching syntax to without.
Adds pattern matching syntax for has_fields.

This also adds it for with_fields since that just rewrites to
has_fields.
made union smarter
Adds functions to order_by.
Adds a GET_FIELD_SHORTCUT flag to func_t.
Adds evaluation for descending terms.
Read the pid only once when stopping an instance

Review 718 by @mlucy
Closes #1115 again
Making the wording more clear, OTS review by @atnnn
Adds evaluation of DESC to order_by.
Make other obj_or_seq functions not recurse on seq of seq.
config file parsing will now ignore options that apply to other modes of rethinkdb
added warning in must specify one of --directory or --file to import when unexpected files are found in the import directory
Make pattern matching work with group_by.
fixed a problem with nice_crash not logging errors properly, although it's pretty ugly right now
stopped using nice_crash in exceptions, just because it's a little silly, unified address in use exception catching, and fixed a bug in object_buffer_t when create() causes an exception
Removed nice_crash and nice_guarantee, since their use case is questionable at best.  Replaced with clean exits, or regular crashes.
Adds tests for without.
Adds tests for pattern matching group_by.
Adds tests for has_fields and with_fields.