Support GEO property and/or geo parameter

[owenh000]

khard 0.17.0 does not offer to add or edit geographical latitude/longitude coordinates, either as a separate GEO property (vCard 3.0 or 4.0) or as a geo parameter (vCard 4.0). Please consider adding support for this in some form, if possible with the underlying vobject library.

Thanks for your work on khard!

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Relevant documentation:

• vCard 3.0 GEO property: https://datatracker.ietf.org/doc/html/rfc2426#section-3.4.2
• vCard 4.0 GEO property: https://datatracker.ietf.org/doc/html/rfc6350#section-6.5.2
• vCard 4.0 geo parameter: https://datatracker.ietf.org/doc/html/rfc6350#section-5.10

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Currently, if the GEO property already exists, the semicolon is escaped when the vCard file is written back out, resulting in an invalid GEO property value.

Input:

BEGIN:VCARD
VERSION:3.0
GEO:0.990000;-0.990000
END:VCARD

Output:

BEGIN:VCARD
VERSION:3.0
GEO:0.990000\;-0.990000
END:VCARD