Combined tasks: Firmware handling with PowerShell

[PeterPawn]

make firmware handling possible under Windows and for other platforms with a bunch of classes for PowerShell Core 6.0

• ~provide a class to handle RSA keys for firmware signing~ - done in signimage/FirmwareImage.ps1 with class SigningKey and some helper classes
• ~provide a class to append, verify, remove a TI-style checksum to/on/from firmware files~ - included in signimage/FirmwareImage.ps1 as TIchksum
• ~read/write/dissect TAR files as base of firmware images~ - done in signimage/FirmwareImage.ps1 as class TarFile with some helpers
• ~add, verify, remove RSA signatures to/on/from firmware images~ - done in signimage/FirmwareImage.ps1 as 'FirmwareImage` class
• read TFFS dumps, create files from it, build TFFS images
• discover starting FRITZ!OS devices
• handle FTP communication with a FRITZ!OS device's bootloader
• handle SquashFS images, extract members, change/add members, if possible
• create scripts to automate the usage of the classes above for various, recurring tasks

[PeterPawn]

Intermediate results are available now in the "eva" branch ... please pay attention to the changed license conditions for files, that are published there.