user interface optimization (done)

# Todo list

## position and space
* position account list and add account buttons centeral-horizontally
* position dialogs centeral-horizontally
* position account detail view central-horizontally
* add padding spaces to bottom, top, left and right borders
* add suitable spaces between controls

## colors and styles
* global theme color is orange:\#F57900
* change dialogs, buttons, checkboxes to orange color

## animations and drawables
* show account avatar if set
* show progressbar when loading

# Useful info
1. on 7” tablets (600dp wide and bigger), use layout-sw600dp to provide layouts, use corresponding drawable-sw600dp-ldpi/mdpi/hdpi/nodpi/xhdpi/ to provide drawables
2. on 10” tablets (720dp wide and bigger), use layout-sw720dp to provide layouts, use corresponding drawable-sw720dp-nodpi/ to provide drawables.
3. for landscape view, use drawable-land-ldpi/-land-mdpi/-land-hdpi/-land-xhdpi to provide drawables

> Older versions (pre-3.2) of the platform will ignore the new qualifiers, so mix them as needed to ensure the app looks great on any device. do it like below.

use layout-xlarge to support pre-3.2 tablets, and layout-sw600dp to support 3.2 and up tablets.