Prevent from freeing objects twice.

When the STL container is being freed, it also frees all the objects which
it stores. We should remember it.
Revert "Prevent from freeing objects twice."

This reverts commit c8de28200a2535982cb91b99a63919298fdbdd36.
Copy constructor and assignment operator for Block class.
Added workaround to .gitignore to store files for Visual Studio 2012 near project without sharing it on repository.
Merge pull request #2 from kkowalczuk/prv-kkowalczuk-unit_tests_issue

Prevent from freeing objects twice.
Merge pull request #3 from kkowalczuk/prv-agajewski-iterator

Backward iterator + unit tests