packed the xml_parser with xml_parser.h in openflow/common dir. scons &
gtest unit supported.
merge kobemiller to master
Merge pull request #13 from zhaonanyu/master

packed the xml_parser with xml_parser.h in openflow/common dir.
Merge branch 'master' of https://github.com/helight/openflow
Merge branch 'master' of https://github.com/helight/openflow into kobemiller
实现agent端task的异步处理，之前的代码先注释掉了，暂时不删除
Merge branch 'kobemiller' of https://github.com/helight/openflow into kobemiller