In plugins config replace "disabled: true" with "enabled: true"

[waldekmastykarz]

Right now, in plugins' configuration we use disabled: true to denote that a plugin is disabled. When skimming through the configuration, you can easily misinterpret it as enabled: true, because true expresses a positive and only by getting the context from disabled you'll see that in fact we mean a negative.

To simplify this, I suggest that we change to enabled: true which is a default on all plugins if omitted in the config. To disable a plugin you'd add enabled: false and the false indicating that the plugin is not running.

Any objections @garrytrinder @sebastienlevert @gavinbarron?

[garrytrinder]

Seems perfectly reasonable.

Ship it 🚀

[sebastienlevert]

No objection!