Added support for /exec

Run a Shell command and display the stdout if everything is Ok.
If the command take more than 10secs to run or the command does not exists or the exit status is not 0 display the error
Use /exec -o to send the output to the channel

Fixed 'ivar' errors.

It's my first Objective-C code. If something is wrong say me, I will try to fix it.

PS: Sorry about possible english mistakes