Transform ColorSchemeEditor class from QWidget to KDialog

Move some code from EditProfileDialog::showColorSchemeEditor
* a part went in the slot EditProfileDialog::saveColorScheme
* a part becomes obsolete since ColorSchemeEditor is the whole KDialog
* a small part went into ColorSchemeEditor constructor

Make ColorSchemeEditor a non-modal dialog : The terminal is not frozen
when the dialog is open
- The Kdialog has an Apply button
- Some safeguard to check that there is only one ColorSchemeEditor open
- Use reference rather than pointer in ColorSchemeEditor interface

Thanks to Renan for improving on Konsole's ColorScheme.

Patch by renan fargetton

REVIEW: 110560
GUI: