Added temporary command x-replace

This runs a search and replace over the entire model.  This is just
temporary at the moment in order to get something working.

Also added hitting backspace on an empty entrybox to cancel it.

ui/stdcomps.go

@@ -4,7 +4,7 @@ package ui
 
 import (
 	"unicode"
-	)
+)
 
 // A text component.  This simply renders a text string.
 type TextView struct {
@@ -124,6 +124,8 @@ func (te *TextEntry) KeyPressed(key rune, mod int) {
 		if mod&ModKeyAlt != 0 {
 			te.backspaceWhile(unicode.IsSpace)
 			te.backspaceWhile(func(r rune) bool { return !unicode.IsSpace(r) })
+		} else if te.cursorOffset == 0 {
+			te.cancelAndExit()
 		} else {
 			te.backspace()
 		}
@@ -136,14 +138,18 @@ func (te *TextEntry) KeyPressed(key rune, mod int) {
 			te.OnEntry(te.value)
 		}
 	} else if key == KeyCtrlC {
-		if te.OnCancel != nil {
-			te.OnCancel()
-		}
+		te.cancelAndExit()
 	}
 
 	//panic(fmt.Sprintf("Entered key: '%x', mod: '%x'", key, mod))
 }
 
+func (te *TextEntry) cancelAndExit() {
+	if te.OnCancel != nil {
+		te.OnCancel()
+	}
+}
+
 // Backspace
 func (te *TextEntry) backspace() {
 	te.removeCharAtPos(te.cursorOffset - 1)