Adding pretty print methods to Dmap classes

From Issue #2 suggestion, added `__str__` and `__repr__`
for better printing of the object that is being used.
Only dmap classes were changed because inherited classes
will obtain the same attributes for printing of the object
but the class name will be adjusted to be same as the actual class
and not the dmap classes.

pydarn/io/dmap.py

@@ -177,17 +177,16 @@ def __init__(self, dmap_file: Union[str, bytes], data_stream=False):
             raise dmap_exceptions.EmptyFileError(self.dmap_file)
 
     def __repr__(self):
-        return "filename: {filename} cursor: {cursor}"\
-                " Record number: {rec_num}"\
-                "total bytes: {total}"
-                "".format(filename=self.filename,
+        return "{class_name}({filename}, {cursor}, {rec_num}, {total})"\
+                "".format(class_name=self.__class__.__name__,
+                          filename=self.dmap_file,
                           cursor=self.cursor,
                           total=self.dmap_end_bytes,
                           rec_num=self.rec_num)
 
 
     def __str__(self):
-        return "Prepared to read: {filename} at cursor: {cursor} "\
+        return "Reading from {filename} at cursor: {cursor} "\
                 "record number: {rec_num} with"\
                 " a total number of bytes: {total_bytes}"\
                 "".format(filename=self.dmap_file,
@@ -865,15 +864,15 @@ def __init__(self, dmap_records: List[dict] = [], filename: str = ""):
         pydarn_logger.debug("Initiating DmapWrite")
 
     def __repr__(self):
-        return "filename: {filename} Record number: {rec_num}"\
-                "".format(filename=self.filename,
-                          rec_num=self.rec_num)
+        return "{class_name}({filename}, {rec_num})"\
+               "".format(class_name=self.__class__.__name__,
+                         filename=self.filename,
+                         rec_num=self.rec_num)
 
     def __str__(self):
-        return "Prepared to write: {filename} at "\
-                "record number: {rec_num}"\
-                "".format(filename=self.filename,
-                          rec_num=self.rec_num)
+        return "Writing to filename: {filename} at record number: {rec_num}"\
+               "".format(filename=self.filename,
+                         rec_num=self.rec_num)
 
     # HONEY BADGER method: Because dmap just don't care
     def write_dmap(self, filename: str = ""):