Output stream can now be set with $outputStream property

[luzrain]

I found out that $outputStream cannot be changed because the property is protected. I need it in my bundle I'm working on.

Changes:

• $outputStream property now public.
• Removed outputStream() getter and moved out $outputStream initialization process from the safeEcho() method to new initStdOut() method.
• Changed the way how the output decoration support is checked. I borrowed it from the symfony console.
• Simplified the resetStd() method and removed the $STDOUT, $STDERR global variables from it.