The two File classes have been enclosed into different namespaces.
To guarantee compatibility with old sketches that uses only one of the two
libraries an additional line:
using namespace xxxxx;
has been added so the users can still use "File" where there is no ambiguity.
BridgeLib::File and SDLib::File classes have been also aliased to BridgeFile
and SDFile respectively, users are encouraged to use that instead of File.
