Cleanup: move Alembic, AVI, Collada, and USD to source/blender/io

This moves the `alembic`, `avi`, `collada`, and `usd` modules into a common
`io` directory.

This also cleans up some `#include "../../{somedir}/{somefile}.h"` by
adding `../../io/{somedir}` to `CMakeLists.txt` and then just using
`#include "{somefile}.h"`.

No functional changes.

source/blender/io/collada/ErrorHandler.h

@@ -0,0 +1,57 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup collada
+ */
+
+#ifndef __ERRORHANDLER_H__
+#define __ERRORHANDLER_H__
+
+#include <string>
+#include <map>
+#include <vector>
+#include <algorithm>  // sort()
+
+#include "COLLADASaxFWLIErrorHandler.h"
+
+/** \brief Handler class for parser errors
+ */
+class ErrorHandler : public COLLADASaxFWL::IErrorHandler {
+ public:
+  /** Constructor. */
+  ErrorHandler();
+
+  /** Destructor. */
+  virtual ~ErrorHandler();
+  /** handle any error thrown by the parser. */
+  bool virtual handleError(const COLLADASaxFWL::IError *error);
+  /** True if there was an error during parsing. */
+  bool hasError()
+  {
+    return mError;
+  }
+
+ private:
+  /** Disable default copy ctor. */
+  ErrorHandler(const ErrorHandler &pre);
+  /** Disable default assignment operator. */
+  const ErrorHandler &operator=(const ErrorHandler &pre);
+  /** Hold error status. */
+  bool mError;
+};
+
+#endif /* __ERRORHANDLER_H__ */