Add property without getter TextView.gravity.

[lukaspili]

As the title says.
Right now, when using gravity inside a textView block, it sets the layout params gravity.
With this modification, there is now 2 different gravity properties:

textView {
   text = "Hello, world"
   gravity = Gravity.CENTER // text gravity
}.lparams {
   gravity = Gravity.RIGHT // layout gravity
}

[yanex]

Merged. Thank you!