improved usability

Fixed console prompt
Fixed cached "ls" command
Fixed incompatibility from jline 0.9.4 -> automatic new line removed
Fixed NullPointerException if no user is given
Fixed NullPointerException if no password is given
Fixed disconnect -> disconnect removes complete session & resets the prompt
Merge commit 'c2b29ffe642d4901ba962e317154a33c8f538414' into HEAD
Releasing new candidate 0.5.31