Readme updates

[j042]

Overview

Updated readme and documentations to give a better overview of this project. I've also included some chores / clean ups here so that examples in readme works as it is.
Changes are:

• more shortcuts. frequently used / main features are directly accessible at splinepy.*
• fitting clean up. tries to use less ifs. It seems that there's an issue with approximation
• microstructure tiles clean up. set some variables as class variable
• added module functions for tiles - easy access to tiles

Checklists

• Documentations are up-to-date.
• Added example(s)
• Added test(s)

[j042]

    @property
    def microtile(self):
        """Microtile that is either a spline, a list of splines, or a class
        that provides a `create_tile` function."""
        if hasattr(self, "_microtile"):
            return self._microtile
        else:
            _log.info("microtile is empty. Please checkout splinepy.microstructure.tiles.show() for predefined tile collections!")
            return None

[danielwolff1]

Looking great, I really really like the modified documentation!

I just had a few minor remarks / questions but generally I approve of the changes made here and you can proceed with the merge! 🚀

[j042]

Todo: background color, in modification plot nr.1 is wrong

[j042]

@jzwar @clemens-fricke are you happy with the background?

[j042]

todo: change extract bases' angle

[j042]

todo: add iges