Fixes and improvements, specially on contrasts and consistency fixes.

• Removed background white accents entirely! Your eyes are now saved!.
• Added comment colors.
• Centered comments.
• Replaced more checkboxes with toggles.
• Fixed checkboxes indeterminate state.
• Improved readability of tabs.
• Improved loading bar.
• Improved dialogs.
• Various other color & style consistency tweaks.