[PATCH]: new dlna_dms_t structure

Specific variables for dms are push from dlna_t into dlna_dms_t variable.
This patch allows to add a future dlna_dmp_t structure for dmp (DLNA Media Player)
Merge branch 'dms_structure' into integration_dms_structure
[PATCH]: dms init all 'dlna_dms_t' variables

dlna_init has not to set dms variables. It's dlna_dms_init which has to set them.
If dlna library has to manage DMP, it's useless to manage DMS
[PATCH]: dms uninit manages dlna_dms_t variables

All dlna_dms_t variables has to be uninit by dlna_dms_uninit function.
For DMP is useless to unset DMS information
[PATCH]: set the default VFS storage

The default VFS storage is "memory". Actualy to set the variable is enought but in future "dms_set_memory" can do more.
Merge branch 'dms_structure' into integration_dms_structure
[PATCH]: set the VFS storage type by default

The default VFS storage is set only the dms variable. But dms_set_memory can do more in the future
Merge branch 'dms_structure' into integration_dms_structure
PATCH : set the playlist for DMP
PATCH : code simplification

dlna_dms_init set the VFS default type to "MEMORY"
the calls to dlna_dms_set_vfs_storage_type set VFS storage set DB if requested.
And fall back to MEMORY if it's impossible
PATCH :  change DLNA_DMS_STORAGE__SQL_DB to DLNA_DMS_STORAGE_DB

SQL_DB is appropriate if we use SQL DB. But DB could be NOSQL DB
moves from dms_set_sql_db to dms_db_open

as the storage type, dms_set_sql_db means we use SQL. But it's false if we want to use NOSQL db in the future.
new DLNA status VFSEMPTY. dlna_db_load load DB to build VFS

dlna.h define he new DLNA_ST_VFSEMPTY, to inform that the VFS is not build.
dlna_dms_set_vfs_storage_type try to load the VFS from the DB and return OK or VFS EMPTY to request the application to build the VFS.
dms_db_load is the new function to load the VFZ from the DB.
Merge branch 'dms_structure' into integration_dms_structure

Conflicts:
	src/upnp_dms.c
new DLNA status VFSEMPTY. dlna_db_load load DB to build VFS

dlna.h define he new DLNA_ST_VFSEMPTY, to inform that the VFS is not build.
dlna_dms_set_vfs_storage_type try to load the VFS from the DB and return OK
dms_db_load is the new function to load the VFZ from the DB.
Merge branch 'dms_structure' into integration_dms_structure

Conflicts:
	src/upnp_dms.c
Merge branch 'vfs_item_id_crc32' into avts
use crc32 as id of the playlit items
add playlist management
avts start a thread to play an item