alembic: Adjust sippeers, queue_members, and voicemail_messages tables.

* Increased the sippeers useragent max string size to 255.

* Changed the queue_members uniqueid to an auto incremented integer
instead of a string.

* Increased the voicemail_messages BLOB size to LONGBLOB on mysql.

* Fixed the add_tables_for_pjsip config change version downgrade actions
to drop a table it created.

* Adjusted the sample alembic.ini files cdr.ini.sample, config.ini.sample,
and voicemail.ini.sample to give a mysql and postgres sqlalchemy.url
lines.

ASTERISK-23847 #close
Reported by: Stephen More

ASTERISK-23825 #close
Reported by: Stephen More

ASTERISK-23909 #close
Reported by: Stephen More

Review: https://reviewboard.asterisk.org/r/3870/
........

Merged revisions 420211 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@420212 65c4cc65-6c06-0410-ace0-fbb531ad65f3

contrib/ast-db-manage/voicemail.ini.sample

@@ -1,3 +1,5 @@
+# A generic, single database configuration.
+
 [alembic]
 # path to migration scripts
 script_location = voicemail
@@ -5,10 +7,17 @@ script_location = voicemail
 # template used to generate migration files
 # file_template = %%(rev)s_%%(slug)s
 
+# max length of characters to apply to the
+# "slug" field
+#truncate_slug_length = 40
+
 # set to 'true' to run the environment during
 # the 'revision' command, regardless of autogenerate
 # revision_environment = false
 
+#sqlalchemy.url = driver://user:pass@localhost/dbname
+
+#sqlalchemy.url = postgresql://user:pass@localhost/voicemail
 sqlalchemy.url = mysql://user:pass@localhost/voicemail