Remove const_contiguous_iterator.

This iterator can be replaced by simple const pointer. To support
comparison operators between basic_contiguous_iterator,
range_snapshotting_iterator and pointers, conversion operator to const_pointer
was added. This change is a potential performance improvement (we don't
have another abstraction layer - const_contiguous_iterator). This also
allows to reduce amount of code.

vector assign API extension

vector: fix asserts which are always true

Fixes inspired by klockwork

test: do not open tx

Do not call methods in tx when not needed or when it is done internally

fix allocation_flag issues

aggregate initialization is allowed for structs with no
user-declared (explicitly defaulted or deleted constructors are
allowed) constructors since C++11, but gcc 4.8.5 doesn't support it

use 'gnutar' archive format for deb package

vector: non-member swap

test: fix pool's layout name

Our swap() implementation is throwing.

vector: add assign methods and operators

vector: rm active tx assert in vector API

verify if non-const access methods/iterators works out of tx scope

it is unsafe to use some access methods/operators (e.g. at(), begin())
out of transaction scope, however we can't forbid users to use them, because there is no other way
to modify elements without transaction

test: cover missing vector cases based on codecov analysis

Add overload for array.range() method.

minor fixes to helper classes

This oveload takes only 2 parameters and snapshots the entire range
immediately. Return value is slice<pointer> instead of
slice<range_snapshotting_iterator<T>>. This change reduces overhead
of moving iterators in case where entire range is snapshotted.

Change array modifiers (assignment operators, swap and fill) behaviour.

Those methods now start internal transaction so that they are seen as
atomic from user's perspective. This behaviour is consistent with
pmem::vector.

Moreover those methods can be called only on pmem-resident objects.
Unlike in pmem::vector we cannot check if object is on pmem in
a constructor (because array is aggregate) so we postpone this to
a swap/fill/operator= function call. This check is performed only
in those functions bacause of performance overhead.