Rewrite compare_date in service_keywords.py

In order to have possibility to compare dates with accuracy passed in
human-readable format

@@ -68,16 +68,54 @@ def get_file_contents(path):
         return unicode(f.read()) or u''
 
 
-def compare_date(date1, date2, accuracy):
+def compare_date(date1, date2, accuracy="minute", absolute_delta=True):
+    '''Compares dates with specified accuracy
+
+    Before comparison dates are parsed into datetime.datetime format
+    and localized.
+
+    :param date1:           First date
+    :param date2:           Second date
+    :param accuracy:        Max difference between dates to consider them equal
+                            Default value   - "minute"
+                            Possible values - "day", "hour", "minute" or float value
+                            of seconds
+    :param absolute_delta:  Type of comparison. If set to True, then no matter which date order. If set to
+                            False then date2 must be lower then date1 for accuracy value.
+                            Default value   - True
+                            Possible values - True and False or something what can be casted into them
+    :returns:               Boolean value
+
+    :error:                 ValueError when there is problem with converting accuracy
+                            into float value. When it will be catched warning will be
+                            given and accuracy will be set to 60.
+
+    '''
     date1 = parse(date1)
     date2 = parse(date2)
+
     if date1.tzinfo is None:
         date1 = TZ.localize(date1)
     if date2.tzinfo is None:
         date2 = TZ.localize(date2)
 
     delta = (date1 - date2).total_seconds()
-    if abs(delta) > accuracy:
+
+    if accuracy == "day":
+        accuracy = 24 * 60 * 60 - 1
+    elif accuracy == "hour":
+        accuracy = 60 * 60 - 1
+    elif accuracy == "minute":
+        accuracy = 60 - 1
+    else:
+        try:
+            accuracy = float(accuracy)
+        except ValueError:
+            LOGGER.log_message(Message("Could not convert from {} to float. Accuracy is set to 60 seconds.".format(accuracy), "WARN"))
+            accuracy = 60
+    if absolute_delta:
+        delta = abs(delta)
+    if delta > accuracy:
         return False
     return True