[FS#1366] dnsmasq documentation consolidation

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - skimj (skimj) 

Attached to Project - OpenWrt/LEDE Project
Summary - dnsmasq documentation consolidation
Task Type - Bug Report
Category - Documentation
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - The documentation for dnsmasq is split between at least 3 pages (and git sources) They are each subtly different, so it's very confusing as a user trying to find information. From a user's perspective, I would suggest that these should be merged to the combined "DNS and DHCP configuration" page but there may be a valid reason to keep them separated that I'm not considering.

In any case, the multiple sources are independent/out of sync which is definitely an issue
[[https://openwrt.org/doc/uci/dhcp|DNS and DHCP configuration]]
[[https://openwrt.org/docs/user-guide/dns_configuration|DNS configuration]]
[[https://openwrt.org/docs/user-guide/dhcp_configuration|DHCP configuration]]
[[https://git.openwrt.org/?p=web.git;a=blob_plain;f=docs/uci_dnsmasq.txt;hb=HEAD|web.git/docs/uci_dnsmasq.txt]]
A couple of simple examples to highlight issue:
  - the description for `add_local_hostname` starts with `Add A, AAAA, & PTR` on some but `Add A, AAAA, and PTR` on others. ("&" vs. "and" isn't an issue as far as content but obviously the data is not sharing a common source)
  - the new (Trunk) option `dhcp_option_force` is on the DHCP configuration page but not in any of the other sources.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1366