Investigate the possibility to use apparently already existing acorn-qml

[ChALkeR]

Moving the discussion from #1.

There are two of those already.

1. https://git.eclipse.org/c/cdt/org.eclipse.cdt.git/log/qt/org.eclipse.cdt.qt.core/acorn-qml by @MattBastien

2. https://github.com/Gaubee/acorn-qml by @Gaubee, based on the one by @MattBastien, with what looks to be some es7-related changes.

   This one was published to npm: http://npmjs.com/acorn-qml.
   The comments for the new code are in Chinese, unfortunately.

Both of those are licensed under the Eclipse Pubic License.

@qmlweb/core, @qmlweb/collaborators, The question is — would we be fine with an Eclipse Pubic License, or should we instead port our own qmlweb-parser to acorn and come up with a different name (#1) instead?

/cc @akreuzkamp @Plaristote @MattBastien @Gaubee

[ChALkeR]

Looks like both those acorn-qml libs are missing some critical functionality that even our qmlweb-parser implements.

• property Item item: Item {} causes an error
• NumberAnimation on x {… causes an error
• InvalidAlias.qml passes when it should fail

We can't use those in their current form, so we should either fork those or start our own from the scratch.