core, bridge: added getFeatures method:

this async method indicate which plugins are activated, and add an additional data dictionary with plugin specific data.
    The result can be general (if profile==C.PROF_KEY_NONE) or specific to profile.

src/bridge/bridge_constructor/bridge_template.ini

@@ -175,6 +175,18 @@ sig_in=
 sig_out=s
 doc=Get "Salut à Toi" full version
 
+[getFeatures]
+type=method
+category=core
+sig_in=s
+sig_out=a{sa{ss}}
+doc=Get available features and plugins
+ features can changes for differents profiles, e.g. because of differents server capabilities
+doc_param_0=%(doc_profile_key)s
+doc_return=dictionary of available features:
+ plugin import name is used as key, data is an other dict managed by the plugin
+async=
+
 [getProfileName]
 type=method
 category=core