[ENHANCEMENT] Merge "Allsky Variables" and "All Variables" tabs in Variable Manager

[EricClaeys]

Having separate Allsky Variables and All Variables tabs in the Variable Manager confuses a lot of people, resulting in extra support. I suggest:

• Merge the tabs. The single tab would have these columns:
  • Variable Name
  • Description (empty if the variable is not defined; variables that are settings could use the Name field in options.json)
  • Format (for variables that are settings we could add this field to options.json to use as the default)
  • Type (empty if the variable is not defined; variables that are settings can use the Type field from options.json)
  • Value (from current All Variables tab)
  • + icon
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• All variables provided by (at least the core) Allsky should start with AS_. Currently the variables in the All Variables tab start with AS_ but not the variables in the Allsky Variables tab. I'm not sure if ${DATE} in Allsky Variables is the same as AS_DATE in All Variables?
• Have multiple tabs containing different types of variables, e.g., Object (sun, moon, satellites, ...), Settings (from settings.json), Actuals (actual values like exposure time), Other.
• All settings.json entries should be variables using the format: AS_S_setting_name, e.g., AS_S_takedaytimeimages, where "S_" stands for "Setting". saveImage.sh would need to export these.
• ALLSKY_* variables we think may be useful to users can have "AS_" prepended to their name, e.g., "ALLSKY_VERSION" would be "AS_ALLSKY_VERSION". Assuming user modules have access to the variables, saveImage.sh could export:
  • ALLSKY_CONFIG ( ? )
  • ALLSKY_DEBUG_LEVEL (so user scripts can write debug statements)
  • ALLSKY_EXTRA (so user scripts know where to write "extra" data to)
  • ALLSKY_OWNER
  • ALLSKY_TMP
  • ALLSKY_VERSION