Update BUILD.md

Overall clean up and correcting typos
Update BUILD.md

Elaborated on the use of build.sh and buildroot.sh.
Merge pull request #17 from Mausy5043/documentation-update

Documentation update
Update BUILD.md

small change
Merge pull request #18 from Mausy5043/documentation-update

Update BUILD.md
Revert "Serial port console freedom"

This reverts commit f624ec9956ab13201d8f4bc718485d21ae11847f.
Merge pull request #19 from Mausy5043/rbelec-master

sync with master