persistent_ptr: add unsigned index operator 1.5

Fix v swap, assignment operators and constructors.

Fix include in one more header

Fix headers inclusion for system headers

Assignment operators didn't work correctly because operatorT()
was not really a const function and this_type (used in those functions)
was not decalared. This resulted in compile error while trying to
assign v<> of different types.

Additionally v<> constructor taking const T& as parameter is not
needed. Using it would mean assigning some value to underlaing val
in v<>, but first call to get() would run constructor (which would
potentially change the value).

Fix typo in pmem::obj::array method description

Add informations about type limitations to persistent_ptr

and specify what is considered as UB by the standard.

Fix include in contiguous_iterator.hpp

Fix array::range() method description

This method does not snapshot the entire range as the comment suggested.
Snaphotting is done inside range_snapshotting_iterator.

Add 1.5 changelog

Klockwork fixes

Because no custom copy ctor/operator was provided copying ctree map
could result in double free.

previously only files passed to add_example were being checked.
This means that all .hpp files were omitted.

which were not added by add_cppstyle

Minor fixes

and reformat those tests

to silence klockwork

common: add missing @file annotations

common: unify include guards

common: create version.hpp file

and names of common files in examples

Find package refactoring