Improve layout editor

[andy840119]

This is how LyricLineLayout loooks like.
Should be moved into Edit/Layout namespace.
.
Also should made a new design.
.
This issue can be separated into several PRs :

• Implement initial screen.
• Implement left side's config.
• Implement right side's preview.
• Adjust right side's lyric preview size.
• Implement manage list of layout, like how translate editor do.
• Make all the feature works.

[andy840119]

Left side should made style like this (see LabelledSlideBar and LabelledTextBox).