[PushHost] Fix issue 87

RSU can now push files to the XBOX DMR.  All that was needed
was to add the ContentLength and ContentType headers to responses
to HEAD requests sent out by RSU.  Actually the ContentLength header
existed before this patch but its value was always set to 0.

This is a port of commit https://github.com/01org/renderer-service-upnp/commit/366171ce9dd1a067af313906c253e111cce5a094

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Build] Enable SOUP session User Agent Customization

- Add the optional --with-ua-prefix flag to allow the customization
of the SOUP session User Agent Customization at build configuration time.

- Construct our user agent prefix with the following template:
%s dLeyna/%VERSION

%s is the value provided --with-ua-prefix if any
%VERSION is the dLeyna version

- Call g_set_prgname(...) API to make our ua-prefix usable by libsoup.

Example:

with ./bootstrap-configure --with-ua-prefix=MypProject user agent value
will be:
  MyProject dLeyna/0.0.1 GUPnP/0.19.4 DLNADOC/1.50

if ./bootstrap-configure is called without --with-ua-prefix, user agent
value will be:
  dLeyna/0.0.1 GUPnP/0.19.4 DLNADOC/1.50

This is a port of commit https://github.com/01org/renderer-service-upnp/commit/a8bf9372b1d4b1373815df265267d0d13c079556

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Bug] Unsubscribe requests are not sent when RSU exits

when RSU exits, send first the requests to unsubscribe
for device contexts notification, and delay the g_main_loop exit
for 1 second to give them a chance to be really sent.

This is a port of commits:
https://github.com/01org/renderer-service-upnp/commit/f66f468445f1f7e7f189c397d366ca4535d9858d
https://github.com/01org/renderer-service-upnp/commit/df7378e9c06a0dba90ac0c9ef84c6d34fb0c2af6

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Device] Make device discovery asynchronous and call GetProtocolInfo

- Make device discovery asynchronous like it is done in MSU:
- add the service task module, device creation is now performed by a
sequence of chained tasks:

GetProtocolInfo, event subscription, Dbus objects publishing.

- The new service-task module is globally the same as the MSU one.

- makefile.am has been updated to include new files:
renderer-service-upnp.h, service-task.h and service-task.c.

- function rsu_async_task_lost_object() remove as it was no more
useful.

This is a port of commit https://github.com/01org/renderer-service-upnp/commit/a756e3b976cfdddea8c9be96586d58f29eebfbbb

Signed-off-by: Regis Merlino <regis.merlino@intel.com>
[Device] Add GotoTrack() player method

- Add a new Player interface method GotoTrack(...) which will
perform a seek operation with "TRACK_NR" unit on the specified
track number.
- Add CurrentTrack and NumberOfTracks properties to the Player
interface.
- API documentation updated
- Tested with Rygel playlist

This is port of commit https://github.com/01org/renderer-service-upnp/commit/8b6ab831433b6883b9857fa3456e690af29696b7

Signed-off-by: Regis Merlino <regis.merlino@intel.com>