Add LCB_OPTIONS environment variable

This option replaces the LCB_COMPRESSION and LCB_SYNCDTOR options and
adds a universal catch all to apply various key-value settings from the
environment, if needed.

None of this is currently documented or intended for public use.

Change-Id: I2646d9a5c7bdfbc030a94c1ee24f35d24f9c2571
Reviewed-on: http://review.couchbase.org/40976
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>