initial implementation of API-REST-collect

The full documentation is available on the forge:
http://forge.fusioninventory.org/projects/fusioninventory-agent/wiki/API-REST-collect
add getRegistryValues() function
support WMI and more
minor
Merge branch '2.3.x' into 2.3.x+collect
Merge branch '2.3.x+collect' into master+collect
Merge remote-tracking branch 'origin/master' into master+collect
drop some debug print
do not use WMI on !Win32
new getInstance function
use getInstance to load backends
split config backends from Config class

This will allow for additional configuration backends later, such as
LDAP for instance.
move scanning code into a scan engine class

This allows to specialise this class into threaded and non-threaded
versions, for easier debugging, and safer usage.
better threads number capping
better variable names
proper method call syntax
useless import
add missing import
useless import
oops, fix module name