3.0 plugin

This reverts backslash to forward slash in vendor namespaced plugin names. It caused problems like having to escape the backslash on command line.

Really sorry about the flip flop guys, but better to admit and fix a mistake now then regret later :)

Fixed in 5d2d9289cbaa213cbc25465eef2f1de059e2c5ea. I had missed @ceeram's comment initially.