logic: added Gradle project setup (issue #379)

* added implementation for Gradle project setup (icon is still missing)
* refactored project loading/saving and SourceGroupSettings
* removed long deprecated Cxx UseSourcePathsForHeaderSearch option

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src/lib_java/project/SourceGroupJavaEmpty.h

@@ -0,0 +1,26 @@
+#ifndef SOURCE_GROUP_JAVA_EMPTY_H
+#define SOURCE_GROUP_JAVA_EMPTY_H
+
+#include <memory>
+#include <vector>
+
+#include "project/SourceGroupJava.h"
+
+class SourceGroupSettingsJavaEmpty;
+
+class SourceGroupJavaEmpty: public SourceGroupJava
+{
+public:
+	SourceGroupJavaEmpty(std::shared_ptr<SourceGroupSettingsJavaEmpty> settings);
+	virtual ~SourceGroupJavaEmpty();
+
+	virtual SourceGroupType getType() const;
+
+private:
+	virtual std::shared_ptr<SourceGroupSettingsJava> getSourceGroupSettingsJava();
+	virtual std::vector<FilePath> getAllSourcePaths() const;
+
+	std::shared_ptr<SourceGroupSettingsJavaEmpty> m_settings;
+};
+
+#endif // SOURCE_GROUP_JAVA_EMPTY_H