tags: Move artist tag to a new header file

I created a new directory for tag related code.  This keeps the core/
directory cleaner and prevents file name collisions between the library
layer and the library tag.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

include/core/tags.h

@@ -6,6 +6,7 @@
 #define OCARINA_CORE_TAGS_H
 
 #include <core/database.h>
+#include <core/tags/artist.h>
 
 
 /**
@@ -33,45 +34,6 @@ enum sort_t {
 };
 
 
-/**
- * Artist tag
- */
-class Artist : public DatabaseEntry {
-public:
-	/** Artist name */
-	std::string name;
-	/** Artist name (lowercase) */
-	std::string lower;
-
-	/** Artist tag constructor */
-	Artist();
-
-	/**
-	 * Artist tag constructor
-	 * @param  name  Artist name
-	 */
-	Artist(const std::string &);
-
-	/**
-	 * Called to access the artist tag's primary key
-	 * @return Artist::name
-	 */
-	const std::string primary_key() const;
-
-	/**
-	 * Read artist information from file.
-	 * @param  file  The file to read from.
-	 */
-	void read(File &);
-
-	/**
-	 * Write artist information to file.
-	 * @param  file  The file to write to.
-	 */
-	void write(File &);
-};
-
-
 /**
  * Album tag
  */

include/core/tags/artist.h

@@ -0,0 +1,48 @@
+/**
+ * @file
+ * Copyright 2014 (c) Anna Schumaker.
+ */
+#ifndef OCARINA_CORE_TAGS_ARTIST_H
+#define OCARINA_CORE_TAGS_ARTIST_H
+
+#include <core/database.h>
+
+/**
+ * Artist tag
+ */
+class Artist : public DatabaseEntry {
+public:
+	/** Artist name */
+	std::string name;
+	/** Artist name (lowercase) */
+	std::string lower;
+
+	/** Artist tag constructor */
+	Artist();
+
+	/**
+	 * Artist tag constructor
+	 * @param  name  Artist name
+	 */
+	Artist(const std::string &);
+
+	/**
+	 * Called to access the artist tag's primary key
+	 * @return Artist::name
+	 */
+	const std::string primary_key() const;
+
+	/**
+	 * Read artist information from file.
+	 * @param  file  The file to read from.
+	 */
+	void read(File &);
+
+	/**
+	 * Write artist information to file.
+	 * @param  file  The file to write to.
+	 */
+	void write(File &);
+};
+
+#endif /* OCARINA_CORE_TAGS_ARTIST_H */