improvements

# Do a round of cleanup in system.css, and ensure code is in the appropriate CSS file.
# Remove code, and possibly entire files, that clearly do not belong, e.g. border, color, font-family, margins, paddings, etc.
# Keep CSS that provides helpful visual cues, and accessibility compliance, such as system messages, progress bars, etc.
# Completely separate admin styles into separate files, i.e. use block.admin.css instead of block.css, when the purpose of the file is purely administrative.

adds additional checkboxes to the permissions form