Implement IEquatable interface

Intended for equality checks, this interface uses
a non-virtual interface idiom.
Implement IPost interface
Implement Post class
Change unit tests architecture

This change enables multi-test suite (multi-file) simultaneous
testing.
Add unit tests for the Post class
Create a Person view and Person window

Intended to show information about a single Person.
Create enums needed by the Person entity
Implement IPerson interface
Implement Person class
Add unit tests for the Person class
Implement post sender and receivers
Implement person posts

Add forward declaration for both person and post
Create a pointer comparison template function
Merge branch 'dev' of https://github.com/aleksandersmierciak/Qt-DbWorkbench into dev