Added Shell back on.
Added shell-specific exception class.
Added synchronizing with double checker for ShellReceiver singleton.
[Shell] Modified IO restrictions.
[Shell] Replaced Vector usages with ArrayList.
[Shell] Refactored 'cd' command implementation.
[Shell] Fixed exception type.
[Shell] Merging arguments for cmd launch to let single command components be passed as different arguments.
Renamed folders. Initializing in current directory.
[Shell] Initializing shell in current directory.
[Shell] Fixed improper File constructor usage
[Shell] Moved CommandType definition to a separate file.
[Shell] Using advantages of canonical path to a file.
[Shell] Moved Command creation logic to CommandSource.
[Shell] ShellReceiver is no longer Singleton. Custom receiver selection available in run(receiver).
[Shell] Modified halt conditions according to the assignment.
[Shell] Renamed constant map according to code style.
[Shell] Redesigned architecture for detecting the number of required arguments for Command.
[Shell] Refactored commands' fileNames' parsing and canonification.
[Shell] Refactored commands' fileNames' parsing and canonification.