Testing using streams for stdout

As we add more we can have them running on different streams and switch between them as needed (Ctrl+N [< or >])
E.G SSD, RAM values, etc
Change from stream manager to panel based, input is now sent to current panel

Each panel has to handle input coming into it (See BasicPanel for example)
Input can be universally handled by RexSimulator.cs
Changed switch toggling from Ctrl+A to Ctrl+S
Moved file upload handling (Ctrl+A) to SerialPort1.cs
Panel output fixes. Code cleanup

Panels now store their output in a buffer, which is sent to stdout when the panel is activated
Quick check to see if file exists in file upload
Moved PanelManager to a static variable in Program.cs