Rewrite for MODX 3

[halftrainedharry]

A rewrite of this extra to run exclusively on MODX 3.

[gpsietzema]

@halftrainedharry wow thanks! Just to be sure: this means we need to have two versions on modx.com I guess? One with compatibility until 2.x and one for 3.x (this one)?

[halftrainedharry]

Yes, I guess so.

As this extra isn't actively developed (no update in 5 years), it seemed more reasonable to rewrite the code completely to MODX 3, than do create a hybrid version for 2.x/3.x.

[domindian]

Thank you halftrainedharry for making this useful extra work in modx3.

But I found a nasty bug. It seems batcher does not update the context when moving resources (changing their parent resource) to (one in) another context. As a result the resources are "ghost" children in the target context and not shown in the resource tree until you either move them back or correct their context_key in the database.

Tested with MODX Revolution 3.2.3-pl.