state ip address on checkin

use submit form, redirecting to show response

config server ssid value should be specified

Without this commit, we cannot connect neurite to ssid which has
uppercase letter in its name.

ref: Semantic-Org/Semantic-UI-Docs#145

update configs to adapt platformio v3.1.0

set default topic in config.json

refactor all config related json stuffs

An important update that discards obsoleted ugly config code.

separate application logic

check wifi status while keep trying mqtt conn

apply fonts and refine charset for page loading

1. make use of base64 to embed inline fonts.
    $ base64 quicksand-v5-latin-regular.woff2 > base64.txt
2. add charset to avoid sluggish page reload.

support config via mqtt

e.g.
mqtt publish -h accrete.org -t /neuro/neurite-000c1632/config/ssid -m 'linkgo.io'
mqtt publish -h accrete.org -t /neuro/neurite-000c1632/config/psk -m 'ilovelinkgo'
mqtt publish -h accrete.org -t /neuro/neurite-000c1632/config/topic_from -m '/neuro/chatroom'
mqtt publish -h accrete.org -t /neuro/neurite-000c1632/config/topic_to -m '/neuro/chatroom'
mqtt publish -h accrete.org -t /neuro/neurite-000c1632/reboot -m "1"