Legacy flag generation

[IohannesIohannium]

Initial support for EU4Vic2 library would use the following structure for each generated polity in common/flag_definitions/00_flag_definitions.txt

[Vic3 tag] = {
    flag_definition = {
        coa = legacy_[XYZ]
        subject_canton = legacy_[XYZ]
        allow_overlord_canton = yes
        priority = 1
    }
    flag_definition = {
        coa = legacy_[XYZ]_monarchy
        subject_canton = legacy_[XYZ]_monarchy
        allow_overlord_canton = yes         
        priority = 20
        trigger = { 
            coa_def_absolute_monarchy_flag_trigger = yes
        }
    }   
    flag_definition = {
        coa = legacy_[XYZ]_republic
        subject_canton = legacy_[XYZ]_republic
        priority = 10
        trigger = { 
            coa_def_republic_flag_trigger = yes
        }
    }   
    flag_definition = {
        coa = legacy_[XYZ]_communist
        subject_canton = legacy_[XYZ]_communist
        allow_overlord_canton = yes         
        priority = 20
        trigger = { 
            coa_def_communist_flag_trigger = yes
        }
    }   
    flag_definition = {
        coa = legacy_[XYZ]_fascist
        subject_canton = legacy_[XYZ]_fascist
        allow_overlord_canton = yes         
        priority = 20
        trigger = { 
            coa_def_fascist_flag_trigger = yes
        }
    }   
}

[XYZ] is the flag code we assign the tag, which it can be the same as the Vic3 final tag (AAC for Aachen) or a CK3 title code (d_northumberland)

[IohannesIohannium]

Note: Textured emblems may not be supported initially

[IohannesIohannium]

The configurable flag_block.txt says for which tags these flag definition lines must NOT be output. For the ones that can be output, the flag-code is thus understood:

• If the country is matched with a CK3 title, use it
• If not, use the country's Vic3 tag (not to use, however, for X## countries)

[IohannesIohannium]

Remind to myself: add a readme to explain how to add new flags to the library, both as images and as blazons

[Zemurin]

We fully support use and reuse of legacy flags via country_mappings.txt's flag = TAG system.