Feature/dsl

[AllanWang]

Resolves #457

This is just an example of kotlin dsl, similar to how materialDrawerKt does it.

Example:

fun Context.example(icon: IIcon) {
    iconicsDrawable(icon) {
        sizeX = sizePx(2)
        sizeY = sizeDp(3)
        val getSizeX = sizeX // Fails; only setting allowed
    }
}

The main difference is that setters are done by var access instead of functions, and variations (eg px, dp, res), are done once and shared, rather than with new functions for each field.

As it stands, if you plan on supporting function variants (sizeDp, sizePx, ...) for all fields, the dsl is not really necessary. However, removing such variations would probably make code suggestions easier.

If you plan on keeping your extensions as is, meaning there aren't shortcuts for each field (eg sizeXDp, sizeXPx), then this might be useful.

Stuff like sizePx can be further shortened to px. It's just that res is shared, so I named it sizeRes and added the prefix everywhere to be consistent

[mikepenz]

https://travis-ci.org/mikepenz/Android-Iconics/builds/549158221#L1392

[mikepenz]

This looks really nice. I like the property approach which can only be set. it makes it look really concise.

Right now I think we should keep the extension functions for the fields in the IconicsDrawable too as people might not use the DSL, but convenience wise we should also make the DSL as nice as possible

[AllanWang]

You can take a look. I added most of the fields, except for shadows since that seems special.

I'm not sure if it's a performance problem that each change causes an invalidation.

Additionally, if certain configurations should not exist along with each other (eg setting icon to IIcon and then setting iconText), then we might want to have multiple dsls.

For now, the icon is the only conflict I see, so I've added them within the initiating functions as opposed to the DSL.