Allow plugins

[jaredreich]

[aziz512]

@jaredreich Here's my implementation of this. Let me know what you think. https://github.com/aziz512/pell/commit/92241c5883dfde8911482372a374923f79727c41

[bcolucci]

I've put some comments in your commit @aziz512. I think that a plugin could just have processing and no icon (no?) Also, you should modify a little the way you load the plugins with promises, in order to keep the plugins initial order (important if there are icons).

[Sjeiti]

Before jumping to conclusions: what is the end goal here?

Shouldn't plugins be something to be used before compilation (as in import myPellPlugin from 'myPellPlugin' (...) pell.init({plugins:{myPellPlugin}})).

Which is already possible for actions if you do import myPellAction from 'myPellAction' (...) pell.init({actions:[myPellAction]}). Although it could use some mechanism with which you add the action to the existing list instead of replacing the existing list.