Correct scancodes for < and >

Source: showkey -s
Report error when lonely < or > is found in send_keys_to_vm

Since < and > are used for special keys (<ENTER>, for example), it is safer to "escape" both < and > keys using <LT> and <GT>.
Added keyboard scancodes for {, [, ], and }
Spawn an I'm-alive loop in the virtual machine
Reduced verbosity (less print calls in process_client_request)
Removed "uptime", added first alive call
Refactoring: moved send commands into array
Added <WAIT_PAUSE> instruction

cryptsetup seems to empty the keyboard buffer when reading the confirmation ("YES").

It may happen that YES is sent to the virtual machine before the keyboard buffer is emptied by cryptsetup.
To avoid this, <WAIT_PAUSE> adds a 2-second delay before sending the next scancodes to the virtual machine.