fix: Deprecate undocumented DatedFormat specifiers

Specifiers *%t, %.t, %_t* are meant for movie titles and are
undocumented for DatedFormat.

- Newly introduced feature to deprecate specifiers is used to inform user.

Closes nzbget#52

VideoSort.py

@@ -906,9 +906,9 @@ def add_dated_mapping(guess, mapping):
     mapping.append(('%_title', title_three))
 
     # title (short forms)
-    mapping.append(('%t', title))
-    mapping.append(('%.t', title_two))
-    mapping.append(('%_t', title_three))
+    mapping.append(('%t', title, 'consider using %sn'))
+    mapping.append(('%.t', title_two, 'consider using %s.n'))
+    mapping.append(('%_t', title_three, 'consider using %s_n'))
 
     # Show name
     series = guess.get('title', '')

testdata.json

@@ -119,13 +119,13 @@
     "NZBPR__DNZB_EPISODENAME": "Let the Children the Childbearers Toil"
   },
   {
-    "id": "dated-1",
+    "id": "dated-deprecated-t-1",
     "INPUTFILE": "The.Daily.Show.2013.06.27.Tom.Goldstein.HDTV.x264-FQM.mkv",
     "OUTPUTFILE": "/dated/2013-06/The Daily Show - 2013-6-27.mkv",
     "NZBPO_DATEDFORMAT": "%y-%0m/%t - %y-%m-%0d.%ext"
   },
   {
-    "id": "dated-2",
+    "id": "dated-deprecated-t-2",
     "INPUTFILE": "Real.Time.with.Bill.Maher.2014.10.31.720p.HDTV.x264-BATV.mkv",
     "OUTPUTFILE": "/dated/2014-10/Real Time With Bill Maher - 2014-10-31.mkv",
     "NZBPO_DATEDFORMAT": "%y-%0m/%t - %y-%m-%0d.%ext"