[subscriber] fix: no return if trySubscribe

missed "return trySubscribe" and also it is better to just start
trySubscribe timer to avoid recursion

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[pkgconfig] qt4 - use contextsubscriber includes

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[cmake] configure *.pc

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[bridge] monitor contextkit config dir

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[loader] migrating to usage of dedicated loaders

statefs-contextkit provider has "qt4" type and qt4 loader is used to
load it

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[bridge] setuid statefs-contextkit-register

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>