Update document and configuration for DHCP lease range

This is my fault and shall be noted at the initial moment, but we need a fix on DHCP lease range configuration.

For now, dhcp-range for the production is defined as:

dhcp-range=133.40.164.1,133.40.164.239,72h
dhcp-range=tag:!known,133.40.164.240,133.40.164.255,6h
dhcp-range=133.40.165.0,133.40.165.254,72h

and this will make

• registered hosts in hosts/macs files are assigned as defined (in two ranges w/o tag:!known)
• registered hosts only in macs files are assigned from two ranges w/o tag:!known
• unregistered hosts are assigned from any range

So, we need to

• add tag:known for two (tag:!known could be better to be kept?)
• if we allow registered hosts in macs (e.g. temporal tool for AIT or engineering) but not in hosts, we shall have a flag to filter and guide them all in specified range

how do you think, all? > cloomis, Yoshida, Hiroshige, kyono