Added a custom widget for tagging dives

A custom tag widget has been added to MainTab.
Tags are seperated by a comma ",". The implementation
supports escaping a comma by using "\,".
While typing, the widget supports the user by suggesting
tags using a QCompleter.

Signed-off-by: Maximilian Güntner <maximilian.guentner@gmail.com>

qt-ui/tagwidget.h

@@ -0,0 +1,26 @@
+#ifndef __TAGWIDGET_H
+#define __TAGWIDGET_H
+
+#include "groupedlineedit.h"
+#include <QCompleter>
+#include <QPair>
+
+class TagWidget : public GroupedLineEdit
+{
+    Q_OBJECT
+public:
+    explicit TagWidget(QWidget *parent = 0);
+	void setCompleter(QCompleter *completer);
+	QPair<int, int> getCursorTagPosition();
+	void highlight();
+	void setText(QString text);
+	void clear();
+	void setCursorPosition(int position);
+public slots:
+        void reparse();
+	void completionSelected(QString);
+private:
+        QCompleter *m_completer;
+};
+
+#endif /* __TAGWIDGET_H */