Fix issue30 color picker pushbutton not work

This issue is related to pixmap based style.
This style only use on Windows and MacOS, thus only these platform run into these problem

The detail can be found here:
http://qt-project.org/faq/answer/why_does_nothing_happen_when_i_set_the_palette_background_color_on_a_qpushb

To solve this, I use stylesheet property instead and solve this issue.
However this cause a little redundant code since we cannot get color in stylesheet.
remove all vtab file
Merge pull request #72 from yodalee/clean-remove-vtab

remove all vtab file
Merge pull request #69 from yodalee/issue30-diagram-colorpicker-not-work

Fix issue30 color picker pushbutton not work
Merge branch 'master' of https://github.com/in3otd/qucs into in3otd-master

Conflicts:
	qucs/qucs/diagrams/diagramdialog.cpp
clean overload virtual warning in components
remove compare int to uint
remove const qualifier unmatch
remove unused parameter in function
remove unused object pointer

replace by foreach
remove unused local variable
fix object initialize order
Merge pull request #76 from yodalee/clean-clang-warning

Clean clang warning
Merge remote-tracking branch 'upstream/master'