add small project for receiving espnow material from a host, transferring it via serial to another esp and finally storing it on a SD card

# Conflicts:
#	client/client/lib/espnow/src/ESPNow.cpp
#	client/client/lib/espnow/src/Message.cpp
#	client/client/lib/espnow/src/Message.hpp
#	client/client/src/main.cpp
#	host/fipy/main.py

move to c++17, change message building, refactored SensorInformation and MeasurementData

See merge request !7

- messages are now built using the constructor
- messages now only contain a single measurement value, even if a sensor might include more than one measurement
- buildMessage has been changed to buildMessages and now returns a list of messages depending on how many measurements a sensor contains
- ClientDataPackage now builds from SensorInformation and MeasurementData
- minor naming refactors

-sensor readout finished
TODO
-implement esp_now protocoll to transfer the Data

# Conflicts:
#	client/client/src/main.cpp

fipy host broadcasts its mac + timestamp on start, main function of client updated according to last commit

Closes #4

Merge Branch `develop` into `sensor_readout`

See merge request !3

add message tests

See merge request !4

# Conflicts:
#   .clang-format
#   .gitignore
#   .vscode/extensions.json
#   .vscode/tasks.json
#   client/client/lib/README
#   client/client/platformio.ini
#   client/client/src/main.cpp

Espnow

See merge request !1

- added test token that allows read/write to
  test bucket

- move data_struct to ClientDataPackage.hpp
- move Message definition to Message.hpp
- move Message code to Message.cpp
- move global time variable to its own namespace called esptime
  - time accessible via esptime::rtc
- Message now uses ClientDataPackage instead of data_struct
- ram_caching now uses ClientDataPackage instead of data_struct
- switched from pointer definition of Message to default constructor
- move headers to hpp files where applicable
- added ArduinoJson library (does not increase space by a lot)