Arithmos: abstract data types API - switching algebra API

[pavly-gerges]

This PR is essentially devoted for the Arithmos APIs:

• [x] Arithmos ADT API.
• [x] Arithmos Switching Algebra Interfaces.
• [x] Arithmos Contiguous Buffers concrete implementation.
• [x] Arithmos Linked Queues provisional concrete implementation.
• [x] Arithmos beginning of Linked Nodes implementation.

In addition to the following utilities:

• [x] Console colors header utility.
• [x] API errno utility.
• [x] Unit Testing utility.