WIP: Issue #483 - Tweaked desktop settings page styles in preparation of further changes

This MR contains the following changes to the desktop settings page:

• Made border radius consistent and applied it where specified in the issue.
  • Added support for detached attribute to <io-list-box> to differentiate between cases where the button is attached to or detached from the list it refers to.
• Made primary blue color consistent across all UIs except the mobile settings page because it is isolated from all other pages and will be taken care of in #591 (closed). The reason for it being that icons/components are used across multiple UIs.
• Removed separators and added hover effects to sidebar.
• Indented section separators.

Marked as WIP for now, while waiting for feedback from Design.