CSS coding style fix.

Remove empty rules, extra empty lines, add semicolon etc.
Update sidebar style.

Smaller the sidebar font to avoild wrapping.
Change hover style as well.
Update table style.

Add a very light background.
Lighter the border.
Update textbox style. Make it more "flat".

Remove box shardow.
Thicker textbox border.
Use Glyphicon to replace Font Awesome.

Glyphicon is the icon font that comes with Bootstrap 3.
Update button style.

Add 2px border.
Use Bootstrap 3’s default rules if possible.
Update paginator style.

Remove border, make it more flat and less bootstrap.
Minor style update.
Make button more rounded.
Add border around paginator.
Remove !important rule in paginator.
Use 1px border around form elements.
Revert chnages in order detail page.
Makr textbox and paginator slightly rounded.
Change some page's icons.

Now all Font Awesome icons are available in Glyphicon.
Add spacing in CSS file.
Remove the last !important rule in CSS.
Merge pull request #643 from kayue/ui/improved-backend

Improved backend UI elements.