Don't upgrade admin hashes into the _users database

Admin users are stored in .ini files and are not full-fledged user
documents. Internally, a fake document is made to allow insertion into
the auth cache. CouchDB 1.6 introduced a feature to upgrade password
hashes from the legacy simple hash scheme to the stronger PBKDF2
scheme. It inappropriately attempted to do this to the fake admin
docs, which do not pass the _design/_auth validation checks. This is
fortunate, however, as CouchDB would then have written the admin users
into the users database causing widespread confusion and fear.
Follow symlinks for space check

Follow symlinks when the compaction daemon checks for available space.

closes COUCHDB-1592
Port 001-load.t etap test suite to eunit
Port 002-icu-driver.t etap test suite to eunit

See setup/0 comment for specific info about loading
couch_icu_driver with eunit.
Port 010-file-basics.t and 011-file-headers.t etap test suites to eunit

Both merged into single suite since they tests single target and shares
common bits.
Port 020-btree-basics.t and 021-btree-reductions.t etap suites to eunit

Both merged into single suite since they tests single target and shares
common bits.
Port 030-doc-from-json.t and 031-doc-to-json.t etap suites to eunit

Both merged into single suite since they tests single target and shares
common bits.
Port 040-util.t etap test suite to eunit
Port 041-uuid.t etap test suite to eunit

Config files are removed in favor of using couch_config API instead.
Port 042-work-queue.t etap test suite to eunit

Etap tests were made in flow style, testing the same things multiple
times without real need. For eunit they are split into small test cases
to focus on testing goals.

Timeout on receive is decreased from 3000 to 100.
Port 043-find-in-binary.t etap test suite to eunit

It been merged into couch_util_tests suite.
Port 050-stream.t etap test suite to eunit
Port 06[0-5]-kt-*.t etap test suites to eunit

All merged into single suite since they're test the same module.
Port 070-couch-db.t etap test suite to eunit

Fix ERL_LIB environment variable setting. Add ?tempdb macros for
unique temporary database name generation.
Port 072-cleanup.t etap test suite to eunit

requests functions from test_util were moved to test_request module
with nicer and simpler API.
Port 073-changes.t etap test suite to eunit

For heartbeats test they don't being counted anymore since their
amount is heavy depends from the overall system performance and some
assertions may fail or not because of that. Instead of this, we just
ensure that their amount is going to increase over the time.
Port 074-doc-update-conflicts.t etap test suite to eunit

Timeout decreased, added 10K clients case
Port 075-auth-cache.t etap test suite to eunit

Timeouts are removed.
Port 076-file-compression.t etap test suite to eunit

The original test suite was decoupled into compaction and comparison
cases.
Port 077-couch-db-fast-db-delete-create.t etap test suite to eunit

Merged into couch_db_tests suite.