Fixes:
* Removed spurious \0 bytes being sent to the client in many cases.
* Properly terminated 404 header.
* Now including Content-length: header for index.html (including built-in).
Clients otherwise had to wait for their own timeout before considering
the page load complete, which resulting in an unpleasant sluggish
experience.
* Switched form submission to GET, as iOS sometimes does not include the
body in the same packet as the POST header, which led to the module
not finding the form values.
* Added redirect after form submission to avoid blank-page-in-browser.
* Moved common "enduser_setup" prefix to a lua_pushfstring() to reduce
string literal overhead.
* Replaced cached lua_State* with calls to lua_getstate(), as in other
modules.
* Fixed broken appending of MAC to the SSID.
* Fixed up macro definitions to not break `if` clauses unintentionally.
Enhancements:
* Support for scanning for available WiFi networks, and picking from the list.
* Support for retrieving the current WiFi station status.
* Added "manual" mode, where the module does not (re)configure the AP setup,
nor shut down automatically. Default is still automatic, as before.
* Updated docs for new `enduser_setup.manual()` function.
Johny Mattsson
Marcel Stör