Implement `Data.read_many`

[GregoryTravis]

Reads a set of files into a table. The result is either one row per table, or the combined contents of all the tables.

Data.read_many
    files:(Vector File)
    format:File_Format=Auto_Detect
    include:Vector File_Attribs=..FileName|..Full_Path|Nothing
    return:Return_As=Merged_Table
    on_problems:Problem_Behavior
    -> Table

Implement File_Format.read_many: like File_Format.read but reads a set of files.

File_Format.read_many
    files:(Vector File)
    on_problems:Problem_Behavior
    -> (Vector Any) ! File_Error