build.sh: Update ovs module name

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
build.sh: Improve ubuntu version detection

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
Fix integer serialisation on 32-bit systems

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
TLV: Document int_to_bin

Signed-off-by: Joe Stringer <joestringernz@gmail.com>
Merge pull request #45 from joestringer/32bit

Bugfix & Document TLV
Merge pull request #44 from joestringer/scripts

build.sh script fixes
Update README.md

Moved the build.sh instructions to the end of the page and brought back the previous ones.
Some newcomers were having trouble with build.sh. The instructions as they are now  will be considered a first step, and the build.sh script will be targeted to developers who need more advanced features.
Removed old POX version that wansn't supposed to be here anymore.