Better doc generation settings.
Add netmask related feature enhancements.

- ip2network: Convert a dotted-quad ip to base network number
- netmask2prefix: Convert a dotted-quad netmask into a CIDR prefix
- subnet2block: Convert a dotted-quad ip including a netmask into a block
- validate_netmask: Validate that dotted-quad netmask is valid
- validate_subnet: Validate that dotted-quad ip and netmask are valid

Also added support for subnet style declarations in IpRange and IpRangeList.

Inspired by a request made by @WlmDH.
Merge pull request #2 from bd808/feature/netmask

 Add netmask related feature enhancements.

- ip2network: Convert a dotted-quad ip to base network number
- netmask2prefix: Convert a dotted-quad netmask into a CIDR prefix
- subnet2block: Convert a dotted-quad ip including a netmask into a block
- validate_netmask: Validate that dotted-quad netmask is valid
- validate_subnet: Validate that dotted-quad ip and netmask are valid

Also added support for subnet style declarations in IpRange and IpRangeList.

Inspired by a request made by @WlmDH.