supported more css units

[Jinjiang]

Support more CSS units without native update.

Three updates together:

1. css-units branch in weexteam/weex-styler
2. weex-next branch in weexteam/weex-vue-loader
3. jsfm-feature-css-units in jinjiang/weex

How it works: CSS value 100rem in <style> will be transformed into "100rem" by weex-styler and then 100 * CSS_UNIT.REM by weex-vue-loader. At the same time define global variable CSS_UNIT in JS Framework. So it works.

[Jinjiang]

alibaba/weex#1894 related

[songsiqi]

OK. Please make sure that all css units in the list are supported by weex-vue-loader and jsfm.

[Hanks10100]

Retain the style units in transformer is fine.

But only change the weex-loader may not support the CSS units very well. The real value of the style needs to be calculated in real time.

Consider this:

<div style="width: {{width}}; height: {{height}}"><div>

this.width = '32rem'
this.height = this.getHeight() / 25 + 'vh'

[Jinjiang]

Just

this.width = 32 * CSS_UNIT.REM
this.height = this.getHeight() / 25 * CSS_UNIT.VH

is OK. The variable CSS_UNIT could be exposed to frontend developers

[Jinjiang]

Another thing is at least we can make it happen before native render support these units. And maybe that's enough already.