also displaying the more specific 'no cpu' error message for servers
reworked file system abstraction layer to support seekable files that were opened in write mode where possible
fixed output rendering in term.write a bit; cleaned up shell execution logic a little (shell.execute now loads the $SHELL directly and runs it with the command that should be performed); added option for a read timeout to buffer:read; primitive variable expansion for default shell (no support for escaped quotes/brackets)