Add commands for some powersave modes

[hybridOL]

These config commands were not yet supported. They cover two of the power save commands with their full functionality. Enums for the parameters have been created.
Moreover, one more getter function for psm state in PVT flags has been added.

[PaulZC]

Hi @hybridOL ,

Thank you for submitting this pull request too. The new code looks good and I will merge it into the next release.

The library already contains a powerSaveMode method, but it includes an additional protocol version check which slows it down. I will update powerSaveMode to use setRXM internally.

SparkFun_u-blox_GNSS_Arduino_Library/src/SparkFun_u-blox_GNSS_Arduino_Library.cpp

Lines 7943 to 7945 in 3416a31

	// Power Save Mode
	// Enables/Disables Low Power Mode using UBX-CFG-RXM
	bool SFE_UBLOX_GNSS::powerSaveMode(bool power_save, uint16_t maxWait)

Also I will change the names, just to make them more self-explanatory: setRXM -> setPowerManagement, setPMS -> setupPowerMode.

Best wishes,
Paul

[PaulZC]

Hi @hybridOL ,

Apologies for the delay!!

Merging...

Many thanks,
Paul