Simplify listGlobalSequences to hasGlobalSequences.

[Mat2095]

• since global sequences are now played all together and can't be played individually, listing them is not very useful, so I replaced listGlobalSequences with hasGlobalSequences to check whether global sequences are present
• renamed onGlobalSequenceChange to onPlayGlobalSequencesChange to reflect the new variable-name

Previously this PR hat more changes, but it was decided to split them into two PRs:

• now you can select different variations for sequences from the drop-down
• renamed params.sequences to params.sequence since it refers to a single sequence and not multiple ones

[Mugen87]

Do you mind if we split up the PR into two 😇 ? I would like to merge point 1 and 2 first.

The third one maybe requires more thought. I'm not sure yet how to manage variations, tbh.

What do you think about making the variations handling more explicit and add a variations drop down if a sequence has variations and maybe add listVariations( id ) on manager level?

[Mat2095]

Do you mind if we split up the PR into two 😇 ? I would like to merge point 1 and 2 first.

Sure, we can do that. What do you mean by point 1 and 2 in that case?

The third one maybe requires more thought. I'm not sure yet how to manage variations, tbh.

What do you think about making the variations handling more explicit and add a variations drop down if a sequence has variations and maybe add listVariations( id ) on manager level?

I thought about that as well. Other viewers switch between variations randomly, but that seems more complicated and I kindof like the idea of being able to choose the variation manually. I had no preference between having having sequence and variation in one list or splitting it into two lists, so I chose the option that seemed simpler. But if you prefer having a separate drop-down, I will do that.

[Mugen87]

Sure, we can do that. What do you mean by point 1 and 2 in that case?

Replace listGlobalSequences() with hasGlobalSequences() and the rename onGlobalSequenceChange () to onPlayGlobalSequencesChange().

But if you prefer having a separate drop-down, I will do that.

Okay, then I would try this approach first and so how it works out.

[Mat2095]

Okay, I've updated this PR to only refactor those two things.
I'll open another PR for the variations when I'm done.