Rename GRUB env utilities

Currently, the utilities used to access both the GRUB and U-boot environments are named identically. This is fine as a first step but I think we need to rename the GRUB ones as I can definitely see a use case for needing both since U-Boot does a lot of other stuff for some platforms.

Reminder: We should make sure the integration check list (and the docs in general) reference whatever new name the tools get.

• https://github.com/mendersoftware/grub-mender-grubenv/pull/16
• https://github.com/mendersoftware/mender-image-tests/pull/51
• https://github.com/mendersoftware/meta-mender/pull/1390
• https://github.com/mendersoftware/mender/pull/770
  • Client
  • rootfs-image-v2
• https://github.com/mendersoftware/mender-docs/pull/1467
• https://github.com/mendersoftware/mender-binary-delta/pull/103
• mender-convert
  • Upgrade tests part: https://github.com/mendersoftware/mender-convert/pull/375
  • Upgrade grub-mender-grubenv version: https://github.com/mendersoftware/mender-convert/pull/375