Updates for v2 of the module

[anmenaga]

Main changes in this: 1) Removed dependency on 3rd party libraries in favor of using .NET Core IoT Libraries. 2) Updated GPIO and SPI cmdlets with new APIs:

• because of specifics of new .NET APIs and to keep cmdlets simple - added new GPIO cmdlet Clear-GpioResources; it is needed in very few situations; majority of scenarios do not need to use it.
• in SPI cmdlets removed Channel and added BusId and ChipSelectLine parameters (because of specifics of new .NET APIs). 3) To align with PowerShell 7.0 release:
• updated TargetFramework to netcoreapp3.1
• updated PackageReference for System.Management.Automation to Version="7.0.0" 4) Bumped ModuleVersion to 0.2.0 5) Replaced tabs with spaces in source code 6) All GPIO, I2C and SPI cmdlets were verified on Raspberry Pi with BME280 and RC522 RFID modules

Fix #21 Fix #48 Fix #50 Fix #49

[anmenaga]

Since you've changed from tabs to spaces, should we have a .vscode folder settings with these common rules?

It would be nice to have this as a separate PR.