Bug Fixes and minor improvements

• Fixed opacity bug.
• Added finer control over blending mode and sampler state.
• Changed progress-bar label to be click-through by default, to make sure the progress-bar can be dragged if not locked.
• Fixed paragraphs that are not left-aligned click and mouse-over detection.
• Fixed combo-box and radio buttons label positioning with global scaling.
• Fixed mouse position on first frame of a new User Interface.