Enable paste of text to the InterceptPlainTextEdit#22

This is a lazy pull request / feature request. For Micro, I'd like students to be able to paste text to the InterceptPlainTextEdit, to check how many characters sent produce an overflow. Here's a suggested patch to `InterceptPlainTextEdit.h` starting at line 41. That works for me, but I'd appreciate help in building the static version so I can distribute the updated version. ``` C++ // Look for a paste command. Since the QTextEdit has editing disabled, // this won't be detected by default. It would be nice if the context // menu also supplied a paste option. if (e->matches(QKeySequence::Paste)) { // Retrieve the text from the clipboard, then send that one // character at a time. QClipboard *clipboard = QApplication::clipboard(); QString originalText = clipboard->text(); for (int i = 0; i < originalText.size(); ++i) { // See emit below. emit keyPressed(originalText.at(i)); } } else { // Do not forward this upward (we don't want local echo) emit keyPressed(e->text()); } ```