Instead of discovering the peripheral database on connection and consuming
the associated resources this will give the user more control over the
discovery operation.
* Adds void NimBLEClient::discoverAtrributes() for the user to discover all
the peripheral attributes as a replacement for the former functionality.
* getServices(), getCharacteristics(), getDescriptors() now take an
optional bool parameter (default false).
If true it will clear the respective vector and retrieve all the respective
attributes from the peripheral. If false it will retrieve the attributes
only if the vector is empty, otherwise the vector is returned with the
currently stored attributes.
* getService(NimBLEUUID), getCharacteristic(NimBLEUUID), getDescriptor(NimBLEUUID)
will now check the respective vectors for the attribute object and, if not
found, will retrieve (only) the specified attribute from the peripheral.
* Exchange map for vector, saving 1,076 bytes of program memory and 5,024 bytes of heap for a small device (LYWSD03MMC)
* Removing m_characteristicMapByHandle (using the handles form m_characteristicVector instead) saving in total (compared to the current master) 1,508 bytes of program memory and 6,500 bytes of heap for a small device (LYWSD03MMC)
* Change NimBLEScan container from std::map to std::vector
* Add function to get advertised device by address
* Update documentation
