New property status bit 'CopyOnChange' is added for any document object
to publish any property as a 'Configuration' option. When Link is
linked to any object with such property, it will duplicate those
properties and added it Link itself as dynamic properties. If the user
changes any of these dynamic properties, the Link will auto copy the
linked to object and apply the new configuration to it.
The Link has a new property 'LinkCopyOnChange' to allow user to
enable/disable this feature.
Spreadsheet's 'Configuration Table' feature will publish its
configuration property with 'CopyOnChange'.
Currently, once the linked object is copied, it will be independent with
the original object. There is no mechanism to auto sync changes back to
the copy.
While executing, Link will look for a special Python callable defined in
the linked proxy object, and run it. This allows for customized link
behavior without defining a specialized Link.
Previous multi-sub-element linking (e.g. Face, Edge) is supported
through SubElements of type PropertyStringList, which does not support
geometry element update tracking. This patch changes it to use
PropertyXLink's new multi-subname capability.
This patch includes the actual implementation of Link, which is
implemented as an extension named LinkBaseExtension in App namespace,
and a full view provider ViewProviderLink in Gui. The reason of not
using ViewProviderExtension is because it need full control when
display, not just extending existing functionalities.
Please see [here](https://git.io/fjPue) for more details of the
implementation.
This patch also includes a set of link manipulation commands, and a
task panel for overriding geometry element colors.
