[splib3] Adds features and one fix

[EulalieCoevoet]

In numerics:

• adds to_degrees() function
• fixes createFromEuler (was modifing the parameter rotation, which is by default given by reference in python)

In animation:

• adds endTime option

[damienmarchal]

Hi @EulalieCoevoet

Thanks for the PR.

Could you elaborate a bit more the use case for the endTime parameter in animate.
It is unclear to me what is its purpose and if its name reflects what it does.

[EulalieCoevoet]

It allows to synchronize and loop multiple animations.

[EulalieCoevoet]

Let's say you have an animation, with a duration of 2s but you want it to play again or rewind every 4s, you'll set :

• startTime = 0
• duration = 2
• endTime = 4

@damienmarchal What do you think ?

[EulalieCoevoet]

What about endDelay with the corresponding new implementation ?

[EulalieCoevoet]

@damienmarchal I've made the changes and added an exemple :)

[EulalieCoevoet]

@damienmarchal can we merge?

[damienmarchal]

@EulalieCoevoet it is ok to me, i just change the code so the parameter is passed as "duration".
If ok to you, you can merge the PR.