containers: fix function to set the id of an empty positions of a PiercedKernel

[marcocisternino]

When a hole is created the setPosEmptyId made the m_ids vector non-coherent. This solution is the simplest one, but the less efficient one when the kernel has to be iterated. This solution solved issues in application using piercedKernel

[andrea-iob]

I've did the following changes:

• checkIntegrirty is now called after every operation performed in the tests;
• fixed the warnings about size_t/long conversion in the new checks of checkIntegrity;
• added some comments in checkIntegrirty;
• updated the commit messages (according to git best practices, the second line of the commit message should be blank);

• the consecutiveness test is now performed only if the kernel is not emtpty (otherwise it will enter in an infinite loop).

[andrea-iob]

Can we merge this?