refs #61, fix locking bug, add write list lock before reintegrating PAIRs into  the cachetable on a open

refs #61, fix some tests, remove checkpoint_callback.cc, as it is not an interesting test, still need t ofix checkpoint_1.cc

 - have closed cachefiles not immedietely free pairs, but set them to the side
 - leave freeing of pairs to the evictor and/or shutdown
 - should a cachefile be reopened before all pairs are freed,
   the pairs belonging to that cachefile are reintegrated into the cachetable

#59 get test_lock_timeout_callback to work with valgrind. change the type of a sync_fetch_and_add from bool to int

Revert "stuff"

This reverts commit 2423c9d0.

fix tests that use it to not need it

 - break up cachetable_flush_cachefile into more digestable functions,
 - decouple hash_id from filenum
 - break up close_userdata into close_userdata and free_userdata

cachefiles_list class and move some functionality in there.

Isolate mempool and OMT into a new class, bndata.
Remove key from the leafentry.

txn object after it commits or aborts

BUILD_TESTING=Off in the cmake config.

properly after a small append into a large append

fixes #70

timing-dependent (though it still is)

and a new operation in test_stress0 for stress testing coverage

fixes #65