UCM12 — change the character base of the string type in the standard annotations

The standard annotations (module ucm_std_ann) defines a set of properties, the type of which is a string (prop_str_t). The base character of this string is “char8”. As these properties are likely to contain text in natural language, it would be better to use wide characters (wchar) instead.

set the character base to wchar in the standard annotations

Issue UCM12-6 is addressed by changing the base character type of string prop_str_t from “char8” to “wchar”.