QCA and SSL certificate initialize can be costly -- so defer
startup of authentication framework until it is actually required.
This has no effect on QGIS desktop, as the news feed request
and other startup network requests will immediately trigger
an initialization of the framework. The use case here is improving
the core application startup time to benefit non-app based clients,
eg. qgis_process.
stored in a single place, and that we always use the default
value when its not overwise set
This has two benefits:
1. The user doesn't see confusing "0" values for radius/length etc,
which are silently treated as some other fixed value when rendering
2. The default values are correctly accounted for when calculating
the layer's AABB, otherwise we end up with a flat AABB by
default
This method will be used where multiple calls to `qgsDoubleNear(x1, y1, eps) &&
qgsDoubleNear(x2, y2, eps) && ... && qgsDoubleNear(xn, yn, eps)` are possible.
