Typescript metadata

[r3mi]

improved TypeScript typings for SymbolMetadata

• added missing booleans dismounted and unit
• added list of allowed strings for affiliation (and base), dimension (and base), condition, context, echelon, and (was missing) leadership

Note : this was reversed from the JS code, perhaps I misinterpreted some things, for example

• I added the strings "" and/or "undefined" as allowed, when it was present in the code: not clear from the code paths which are really allowed values from getMetadata()
• I added "LandDismountedIndividual" for dimension (but not baseDimension)

Also : there is a typo in baseAffilation (missing an 'i' : should be baseAffiliation) but I didn't fix it, to not impact the API