Reward tube

Use the rewarder module to create reward tubes. The typical use case is the following: You are supposed to spend X hours on a task. For each hour spent, award yourself with a coin. You are allowed to freely spend the collected on anything you like once the tube is full.

You can define different rewards for various types of tasks. You could give yourself several coins for one achievement, use tokens, use different coins, etc.

By default, the width is adapted to 1 Euro. It is easy to adapt the width of the tube to other coins. You also can add other currencies. All you need to do is to look up or measure its width and thickness and add a line of code or use one of the customizer options (see below).

Other parameters fix wall size, floor size, front/back gap, corner radius, text on side and floor, etc. Sorry, the customizer does not seem to work here. It does work in OpenSCAD 2018 dev.

If you prefer a reward tube with an attached box, see [this reward box](https://www.thingiv