Added opening connector to IGV component (#522)

[alexandreh-met]

Goal

Added an opening connector to the IGV component and modify the gas turbine examples accordingly.
Resolves #522

Type of change

• Bugfix
• New feature
• Refactoring change
• Release & Version Update (don't forget to change the version number in package.mo)

Will it break anything in previous models ?

• Breaking change (If yes, make sure to point it out in the changelog)
• Non-Breaking change

Checklist

• I have added the appropriate tags, reviewers, projects (and detailed the size and priority of my PR) and linked issues to this PR
• I have performed a self-review of my own code
• I have checked that all existing tests pass
• I have checked that my work is compatible with OpenModelica
• I have added/updated tests that prove my development works and does not break anything.
• I have made corresponding changes or additions to the documentation (in Notion documentation)
• I have added corresponding entries to the Changelog
• I have checked for conflicts with target branch, and merged/rebased in consequence

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[nabily-met]

I would say this is a breaking change. Models that has an IGV component should now connect them to an opening sensor or and equation will be missing.

[alexandreh-met]

:)