Rename LineEditFocusWidget to RDLineEdit

* It seems due to deficiencies in Qt's design, there will be a
  substantial need for these small custom subclasses just to add basic
  functionality that should have been present in the original. So we'll
  adopt a naming scheme of QFooBar -> RDFooBar for this 'almost the
  same widget' type subclassing, compared to more custom/changed ones.

qrenderdoc/Widgets/RDLineEdit.cpp

@@ -0,0 +1,21 @@
+#include "RDLineEdit.h"
+
+RDLineEdit::RDLineEdit(QWidget *parent) : QLineEdit(parent)
+{
+}
+
+RDLineEdit::~RDLineEdit()
+{
+}
+
+void RDLineEdit::focusInEvent(QFocusEvent *e)
+{
+  QLineEdit::focusInEvent(e);
+  emit(enter());
+}
+
+void RDLineEdit::focusOutEvent(QFocusEvent *e)
+{
+  QLineEdit::focusOutEvent(e);
+  emit(leave());
+}