(fwPreferences): add password management capabilities
Description
Currently there is no way to manage a password in sight. We need to be able to keep a password so it can be passed to other services (and used, for example in SWriter or in SReader to allow encryption). We also need to store the hash into preferences so it can be checked later and ensure the one entered by the user is correct.
Proposal
The idea is to provide this group of functions :
/// Set the password to use in the application. If null or empty, erase it.
FWPREFERENCES_API void setPassword(const std::string& password);
/// Return the password used in the application.
FWPREFERENCES_API const std::string getPassword();
/// Check if the given password match the hash stored in the preferences
FWPREFERENCES_API bool checkPassword(const std::string& password);