feat(st): update stm32image tool for header v2

feat(st): update stm32image tool for header v2

The stm32image tool is updated to manage new header v2.0 for BL2
images.
Add new structure for the header v2.0 management.
Adapt to keep compatibility with v1.0.
Add the header version major and minor in the command line
when executing the tool, as well as binary type (0x10 for BL2).

Change-Id: I70c187e8e7e95b57ab7cfad63df314307a78f1d6
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>