Add interface for queue type

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add queue.c file with stubs

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add implementation for ws_queue_init()

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add implementation for ws_queue_new()

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add deinit callback

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add implementation for ws_queue_push()

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add implementation of ws_queue_pop()

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add implementation for ws_queue_empty()

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add testing file for queue tests

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add init test

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add new-queue test

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add queue pushing test

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Add queue pop test

Pair-programmed-with: Marcel Müller <com2040@gmail.com>
Merge pull request #598 from matthiasbeyer/add-ws_queue

Add ws_queue type