Synfig: Waypoint types list is not consistent across Synfig Studio

[FirasH]

Synfig version & platform:
Master: 4f6e09

Issue description:
In Synfig Studio there are various places where the user can choose the type of waypoint to use.

I have noticed that those lists are not always consistent.

For example in the timeline we have:

While editing a specific waypoint the order is different:

Probably there are other places where this order is not consistent. It would be nice to have it consistent across all Synfig Studio.

[FirasH]

I can work on this.

I think we could order them using alphabetical ordering i.e.
Clamped / Constant / Ease In/Out / Linear / TCB
but this will be true for sure only for English.

Alternatively the order could follow the likelihood of using a type of interpolation, but still that depends on the animation project.

What would you suggest?

[Hari-07]

if its not already done, i'll work on this

[ice0]

@UltimateGamer07 @FirasH already done it #1245 (just waiting for review)

[morevnaproject]

I like the order done by @FirasH: Clamped, TCB, Constant, Ease, Linear