README: Updates to the README file for OpenMAMA 2.3.0 release.
README: Updates to the README file for OpenMAMA 2.3.0 release.

A number of updates to the OpenMAMA README file to capture changes
for the 2.3.0 release. These include updated web references, some
additional information and details on building OpenMAMA with scons.

Signed-off-by: Damian Maguire <21930bd10afdadbc1f53edcd2634e8f66a5e6d7a@nyx.com>

fquinner/OpenMAMA,philippreston/OpenMAMA,philippreston/OpenMAMA,jacobraj/MAMA,MattMulhern/OpenMAMA,jacobraj/MAMA,philippreston/OpenMAMA,dmaguire/OpenMAMA,dmaguire/OpenMAMA,fquinner/OpenMAMA,dmaguire/OpenMAMA,philippreston/OpenMAMA,kuangtu/OpenMAMA,dpauls/OpenMAMA,dpauls/OpenMAMA,MattMulhern/OpenMAMA,fquinner/OpenMAMA,dmaguire/OpenMAMA,philippreston/OpenMAMA,dpauls/OpenMAMA,dpauls/OpenMAMA,jacobraj/MAMA,fquinner/OpenMAMA,kuangtu/OpenMAMA,dmaguire/OpenMAMA,jacobraj/MAMA,dmaguire/OpenMAMA,kuangtu/OpenMAMA,kuangtu/OpenMAMA,MattMulhern/OpenMAMA,fquinner/OpenMAMA,dmaguire/OpenMAMA,MattMulhern/OpenMAMA,dpauls/OpenMAMA,fquinner/OpenMAMA,jacobraj/MAMA,philippreston/OpenMAMA,kuangtu/OpenMAMA,kuangtu/OpenMAMA,MattMulhern/OpenMAMA,fquinner/OpenMAMA,dpauls/OpenMAMA,dpauls/OpenMAMA,jacobraj/MAMA,kuangtu/OpenMAMA,MattMulhern/OpenMAMA,philippreston/OpenMAMA,MattMulhern/OpenMAMA