Storing opened files paths

[shujaat-github]

Just like storing open handles using GetContext()->m_open_handles.insert(handle); I want to store file paths too so that I may check which specific files are open before unmounting drive. I noticed that at the moment when handle is stored, FileName is just L"\\".

@bailey27 can you please guide me how to achieve this? or better add this support in cppcryptfs.