add "Augment disable" and "Augment enable"

[dannys42]

To make it possible to enable or disable based on autocmd. Also would be nice to be able to configure whether it is disabled or enabled by default.

(see https://stackoverflow.com/questions/3368184/disable-vim-plugin-for-certain-filetypes)

[NobbZ]

Personally I disable (actually enable) per project by using conditionals in my lazy loader.

#6 (comment) shows an example of this. Under the hood I am using lz.n. I am pretty sure other lazy loading mechanisms have similar capabilities.

But yeah, once it is loaded, augment seems to aggressively use any file you open to build up its context.