core: Allow arbitrarily large config values
core: update lager_file_backend configuration to new format.
core: Upgrade config schema on install to allow arbitrarily long config values
core: Make z_db:update/4 more robust when the updating props column
mod_admin: Fix fluid colum layout
mod_admin: more tweaks
mod_admin: more tweaks

includes improvements to headers in widgets
mod_mqtt: integrated mqtt support.
This optionally starts a MQTT listener, using emqtt.
The MQTT router is shared between sites, each adding their own topic tree.
Browser pages have their own simple local routing mechanism, and can dispatch observe or publish commands to the server's router.
Communication between the server and pages is done using the normal event mechanism, where payloads are encoded using UBF(A).

Issue #642
core: fix include of mqtt header file.
core: rename mqtt auth module to something emqtt expects.
core: Allow passing options to z:m. For example z:m([{d, 'TEST']) enables eunit tests.)
mqtt: better access check integration with the mqtt listener.
mqtt: missing from last commit.
core: start with better handling of page process re-starts.
core: also stop emqtt before stopping mnesia.
mod_mqtt: add simple record/object mapping to ubf.js
mod_mqtt: remove console.log, update todo-list
Merge branch 'mw-mqtt'
mqtt: fix include paths for Travis CI clean builds.
mod_bootstrap: update to bootstrap v2.3.2.

Fixes #641.