SCM: add common_names tab (#4657)

[xLPMG]

This PR adds a "Common Names" tab to the sky culture editor, which lets the user insert cultural names of stars, plansts and DSOs

Fixes #4657

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update
• Housekeeping

How Has This Been Tested?

Created different sky cultures on my macbook.

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (header file)
• I have updated the respective chapter in the Stellarium User Guide
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[xLPMG]

I'm not 100% sure what the most intuitive workflow is. Currently possible:

1. To create a new name: Fill data --> Press "Add Entry" -> repeat
2. To edit a name: click in list on common name, then press "Load selected" to load data or simply fill from scratch -> Press "Save Entry" to override or "Add Entry" to add as a new name