move repo, ssid, and bssid to static vars in FDroidApp

Since there is only one local, device repo for swapping, it makes sense to
represent it using static variables in the Application subclass.  It makes
the code a lot simpler too.

FYI KerplappApplication will become FDroidApp once integrated.
move LocalRepoService handling to FDroidApp

This provides very easy to use way to start, stop, and restart the local
repo from anywhere in the app, without needing any special context or info.

refs #2908 https://dev.guardianproject.info/issues/2908
WifiStateChangeService/Receiver for broadcasting network update triggers

Get the WiFi state changes from the system, if that results in a new
connection, then send a local broadcast to tell everything to update.

fixes #3201 https://dev.guardianproject.info/issues/3201
QrWizardWifiNetworkActivity enables wifi and starts the webserver

This makes it less button clicks and things to remember when going through
this process.
move all QR Code image generation into AsyncTask to keep things snappy

Generating the QR Code image can take some time, so do it in an AsyncTask
which then updates the ImageView once the QRCode is complete.

refs #3201 https://dev.guardianproject.info/issues/3201
only trigger WifiStateChangeService when wifi is enabling or enabled

WifiStateChangeService waits for WiFi to be enabled and set up with an IP
address before it will continue.  Therefore, only trigger it when WiFi is
already enabled or in the process of becoming so.  Otherwise, no need to
worry since WifiStateChangeReceiver will trigger whenever wifi is connected.

This also adds a new trigger to the "Use HTTPS" preference, so that it will
take effect immediately when the checkbox is changed.