Add in-app DUART port terminals

[GoLoT]

Add widgets to send and receive input to and from DUART ports without external tools.

[GoLoT]

Added in-app DUART terminals when BSVC_GUI "Title" is passed as command for the DUART port.

TODO:

• Add support for characters other than A-z, space and enter.
• Test thoroughly.

[M-T3K]

Should also allow sending input in batches (For example, repeat char sequence several hundred times automatically)