Several issues fixed

[mikeofqyn]

Fixing #7, #21, #20 and (partially) #19, #28

Issue #21 (issues with newer esp8266 Arduino cores 3.0.x)

Changed the ESP8266 core CoogleIOT::checkForFirmwareUpdate() to replace the call to the deprecated and removed (since version 3.0) ESPhttpUpdate::update() with the currently supported function ESP8266HTTPUpdate::update().

The member function bool CoogleIOT::verifyFlashConfiguration() lacks a 'return ` statement causing the code to crash on return. Added the The ESP exception decoder does not help too much, by the way, as it locates the fault elsewhere.

Issue #7 (configuration when wifi config is invalid)

The problem lies in CoogleIOT::loop() trying to reconnect and resetting over and over again rendering the library unable to process configuration portal requests.

A new member function has been added, CoogleIOT::loopWebServer() to be used in a loop when connection cannot be established. Its use is demonstrated in the DHTSensor.ino sketch in the examples folder.

Issue #19 (Custom items)

Two application specific fields, up to 25 character long have been added to the configuration portal interfacew (MQTT tab). They can set and retrived via new API calls. Their names (used as labels in the configuration portal) can also be set. Usage is shown in the DHTSensor.ino example.

--- Other ---

• Changed version number to 1.3.2.
• Added an example (DHT11Sensor.ino) showing the new features
• Merged #20 (depends=PubSubClient in library.properties).
• Partially implemented #17, adding additional checks to avoid crash in CoogleIOT::loop()
• Update README.md and keywords.txt with the changes.

[amaillo-coop]

Thanks for fixin #21 !! This PR needs to be merged.