Wrap library into namespace hpp.

* Commands executed:
* find include src test -iname "*.h" -type f -exec sed -i "s/^namespace fcl/namespace hpp\n{\nnamespace fcl/; \$i} // namespace hpp\n" {} \;
* find src -iname "*.cpp" -type f -exec sed -i "s/^namespace fcl/namespace hpp\n{\nnamespace fcl/; \$a\\\n} // namespace hpp" {} \;
* find test/ -iname "*.cpp" -type f -exec sed -i "s/using namespace fcl/using namespace hpp::fcl/; s/fcl::/hpp::fcl::/g" {} \;