Reads an object from the given file
The opposite of DictImport.saveIdx. Reads the index located in the first part of the index file into the internal map m_index and estimates the position of the begin of the DictEntryRef array in m_arraybegin. The progress of the reading process is populated using IProgress.progress() of the progress handler m_progresshandler. After the method is ready, it calls IProgress.ready(), either with null as argument, if everything went OK or with the exception string, if errors occured. The path for the dictionary file located in the index file may be evtl. icorrect, if the dictionary file can't be found, then the method tries to find it in the dicrectory of the index file or in the directory of the executing assembly.