Add support for smart playlist manipulation by date added to database. Updated mt-daapd.playlist to match

contrib/mt-daapd.playlist

@@ -20,13 +20,16 @@
 #   Orchestra (string)
 #   Conductor (string)
 #   Grouping (string) -- I don't even know what this is...
+#   Comment (string)
 #   Year (int)
 #   BPM (int)
 #   Bitrate (int)
+#   Date (date)
 #
 # Valid operators include:
 #   is, includes (string)
 #   >, <, <=, >=, = (int)
+#   after, before (date)
 #
 # the "is" operator must exactly match the tag,
 # while the "includes" operator matches a substring.
@@ -69,6 +72,52 @@
 # orchestra or conductor... this would probably include any
 # orchestral music.  Kind of ugly, but works!
 #
+#
+# DATES
+#
+# Dates are kind of funky.  The "date" of a file is when it
+# was created on the file system, or the date that it was first
+# entered into the database, whichever is earlier.  The date of 
+# a file can be matched with the terms "before" or "after".
+#
+# One example of a valid date is a date in yyyy-mm-dd format:
+#
+# "Files added after January 1, 2004" {
+#   date after 2004-01-01
+# }
+#
+# There are also some special date keywords:
+#  "today", "yesterday", "last week", "last month", "last year"
+# 
+# A valid date can also be made by appling an interval to a 
+# date.  As an example, a valid date might be:
+#
+# 3 weeks before today
+# or
+# 3 weeks ago   
+#
+# You can combine these, of course.
+#
+# "3 weeks before today" is the same as "2 weeks before last week" 
+# or "1 week after last month" or "21 days before today" or
+# "20 days before yesterday" or "7 days after last month".  You get
+# the idea.
+# 
+# Note that the playlists are only generated at the time that mt-daapd
+# starts... so while the dates will be accurate at start time, they
+# may become inaccurate with time.  Yes, I know... it's on my list.  :)
+#
+# So, examples:
+#
+# "Recently Added MP3s" {
+#   date after last month AND file includes ".mp3"
+# } 
+#
+# This matches only mp3 files added in the last 30 days.
+#
+# 
+# SUMMARY
+#
 # I expect that this language will grow over time.  If you want
 # to hack on it, see src/lexer.l, src/parser.y, and src/playlist.c
 #
@@ -77,22 +126,19 @@
 #
 
 "60's Music" {
-	Year > 1959 && Year < 1970
+    Year >= 1960 && Year < 1970
 }
 
-"70's Music" {
-	Year > 1969 && Year < 1980
+"Recently Added" {
+    Date after 2 weeks ago
 }
 
-"80's Music" {
-	Year > 1979 && Year < 1990
+"Non-DRMed Music" {
+    path not includes ".m4p"
 }
 
-"90's Music" {
-	Year > 1989 && Year < 2000
+"AAC Files" {
+    path includes ".m4p" ||
+    path includes ".m4a" ||
+    path includes ".aac"
 }
-
-"00's Music" {
-	Year > 1999
-}
-