Request: update IotWebConf2 to match IotWebConf, and upgrade tinyGS

[andypiper]

Currently, the project appears to consume a forked version of the IotWebConf library. This is slightly out-of-step with the upstream version. It also seems to need to be copied manually into the tinyGS working tree in order to be used.

I've worked to update a local copy, as I wanted to inherit some of the upstream improvements to things like mDNS, this has been a bit hacky though so it would be great to see things improved here.

A few notes:

• I found that the major incompatibilities between IotWebConf and IotWebConf2 / tinyGS are the updates to move the constants like IOTWEBCONF_STATE_ONLINE into enums iotwebconf2::NetworkState::OnLine; also, there's a need to handle the update page more directly. More in their the IotWebConf migration documentation.
• Ideally, the project would include this (and other libraries) as submodules at a pinned git version, rather than requiring them to be copied in
• Doubly ideally, it might be a good idea not to depend on a forked version if the changes in IotWebConf2 could be accepted upstream.

[andypiper]

BTW I put this issue here instead of on IotWebConf2 since that repository does not have Issues enabled, but it seems like it mostly (only?) exists to support this project, so this seemed to make sense.