@pavelvasev merge: Component context optimization.. maybe we do not need it?

[ChALkeR]

if we create context for every createComponent call, maybe it is too
heavy... So we introduce option to provide context in createObject
method which overrides it's component context.

This merges 871fbf0, ref: #32.

/cc @pavelvasev @Plaristote

[Plaristote]

Well, it LGTM.
But there's not much left of the original commit, and I'm wondering if the message is still appropriate for the changes that are made in here. The component cache is gone, the only thing added is the ability to overload the context that createObject usually uses, right ?

[ChALkeR]

@Plaristote Thanks! I will amed the commit message.

[ChALkeR]

Ok, everything is good here, landing.

[ChALkeR]

For reference, this removes usage of non-standard second parameter of Qt.createComponent, which was removed in ff4002c.