DIOT SB repository preparation for v3

This MR deals with the following topics:

• The project should now be completely decoupled from its name and version (issue #81 (closed))
• The gateware now generates automatically the top-level block design wrapper (issue #83 (closed))
• Removed obsolete top-file diot_v2_top.vhdl from the project
• Removed unnecessary device-tree compilation patch for U-boot
• Changed the recommended cleaning command for out-of-date gateware suproject from make distclean to make mrproper
• Fixed the U-boot CI stage needing to re-generate the device tree (issue #85 (closed))
• Makes tamper warnings be redirected to stderr (issue #90 (closed))

MR left in draft until testing is done. Board boots and has ethernet. diot_util output seems correct.