Add concurrent_hash_map usage example for doxygen

Increase timeout for valgrind tests on travis

test_package and test_findLIBPMEMOBJ_cmake runs use libpmemobj 1.4

So that concurrent_hash_map_drd tests will not fail.

Remove unnecessary #include <libpmemobj.h>

Node std layout

remove TTB info from README

Update appveyor to use PMDK v1.7

concurrent_hash_map: introduce internal scoped_lock_traits

it is outdated and redundant

To achieve that classes node and hash_map_node_base was merged into one
class hash_map_node.

to generically implement upgrade/downgrade operations. If scoped_lock_type
implements upgrade_to_writer and downgrade_to_reader then traits class
will just call those methods, otherwise it will provide default implementation.

Fix persistent_pool_ptr swap() method signature

Do not allow concurrent_hash_map concurrent methods in a transaction

to make sure it is consistent in singlethreaded methods like clear()
and assignment operators in case of transaction abort.

All methods that take locks on bucket/elements MUST NOT be called in
a transaction. If this was allowed, transaction could abort after releasing
locks and values would be modified without holding a lock.

Hashmap code cleanup

concurrent_hash_map: introduce version field and add reserved space

Fix array move assignment operator

conditional_add_to_tx can throw an exception which means swap()
should not be noexcept.

to make sure that data was create using the same (or compatible) version
of concurrent_hash_map.

Also change order of some members so that embedded_segment (which size is
dependent on size of the mutexes used is at the end). This allows to have
segment_enable_mutex aligned to cacheline.

* Expect bucket bucket to be already locked inside get_node().
* Move logic for restarting search after mask race to internal_find/insert.

explaining that it does not add moved-from array to the transaction.
Also add test for move ctor.

Until now, move assignment for array performed copy instead of move.
Fix this issue and add test for move assignemt.

Update doxygen files

This function should only be called after modification (only in internal_insert).

concurrent_hash_map: pass reference to bucket instead of pointer in get_node

Copied from pmem/pmdk.

Using uint64_t removes padding.

get_node() expects pointer to bucket_accessor to always be set, so it's safer to
use reference.