Includes some fixes but mostly code was refactor to allow easier introduction of new features and completely rewrite of SFTP along with fixing a bug for uploading huge files
1. Complete rewrite of SFTP to allow full asynchronous command execution.
2. SFTP Download and upload command allow to report number of bytes downloaded or uploaded using SftpAsynchResult class. (examples will be added later)
2. Add shell class which allows to implement basic terminal functionality;