Remove old leftovers auto-generated GATT UUIDs

The Bluetooth SIG kept changing their website describing the assigned GATT
services and characteristics UUIDs. Because of that I had to commit a static
version of the `gatt.inc` file instead of creating it during build so
compilation won't fail.

Don't wait for ESP_GATTC_WRITE_DESCR_EVT

On some devices, when enabling notifications on the Services Changed
characteristics the ESP_GATTC_WRITE_DESCR_EVT event isn't received blocking the
BLE queue even though it was seen with a BLE sniffer that the peripheral did
respond to the write request.
As a workaround, we'll not wait for this event and simply dequeue the next
operation.

Fixed compilation errors/warnings

Fixes shmuelzon#41

Temporarily commit auto-generated code

The Bluetooth SIG has changed their website and have a few issues with the list
and definitions of the GATT services and characteristics. Until this is sorted
out I'm committing the auto-generated code and will revert this commit once the
site is working properly.

Fixes shmuelzon#31

Use ESP-IDF's built-in HTTP client

Periodically purge non-connected devices

This should avoid running out of memory when the discovered devices list keeps
growing.

Inlcude free memory in heartbeat publications

Upgrade to ESP-IDF v3.1.3

Disable WiFi modem sleep

This will lower the latency a bit when sending commands (read/write) to the
ESP32.

Fixes shmuelzon#29

Added Mijia Temperature + Humidity broadcaster