Add more meaningful default less(1) options

The following options are maintained in the LESS environment variable
and are supported by all modern implementations of less(1) in case we
end up with nothing but the root partition mounted in single user mode.

 * -s   Squeeze blank lines
 * -i   Case-insensitive search (unless we type uppercase letters)
 * -R   Display ANSI color escape sequences
Add llp (paginated ls -l output)
Use less(1) as man(1)'s pager

As man is already an alias, the easiest way to achieve this is to pass
the -P (pager) option to man(1), which overrides the PAGER and MANPAGER
environment variables.