Allow batch_sign to process files/directories recursively

[enaess]

It would significantly help us perform post build signing if the CodeSignTool could process the input directory recursively and ignore files that it doesn't support.

For example,

input-directory-unsigned
    + i18n/
        + ja/
            comp1-resource.dll
            comp2-resource.dll
            comp3-resource.dll
        + de/
            comp1-resource.dll
            comp2-resource.dll
            comp3-resource.dll
     comp1.exe
     comp2.exe
     comp3.dll
     comp4.dll 
     comp5.exe
     ...

Should have a mirrored output

output-directory-signed
    + i18n/
        + ja/
            comp1-resource.dll
            comp2-resource.dll
            comp3-resource.dll
        + de/
            comp1-resource.dll
            comp2-resource.dll
            comp3-resource.dll
     comp1.exe
     comp2.exe
     comp3.dll
     comp4.dll 
     comp5.exe
     ...

Instead of error out of the batch_sign process when encountering a file that it doesn't know how to handle, print a warn/debug message into the logs and skip processing the file.