Migrate from Poco::File and Poco::Path to std::filesystem - c++17

[peterfpeterson]

Describe the outcome that is desired.
As of C++17 std:filesystem has the necessary functionality for most filesystem operations. Move from using Poco to using the std library.

Recipies for migrating

• Poco::File(filename).exists() -> std::filesystem::exists(filename)
• Poco::File(filename).isDirectory() -> std::filesystem::is_directory(filename)
• Poco::File(filename).remove() -> std::filesystem::remove(filename)
• Poco::File(filename).createDirectory() -> std::filesystem::create_directory(filename)
• exceptions generated are std::filesystem::filesystem_error
• extension = "." + Poco::Path(filename).getExtension() -> extension = std::filesystem::path(filename).extension().string()

some common std::filesystem operations

See EWM 7150