[subprocess] error reporting for qt5v8

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[util] eachProperty and eachPropertyUntil

To allow explicitly use this type of enumeration if X.each() is not
working for some reason

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[util] better dump()

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