Added a document on the requirements and design of the HA features.
Added a document on the requirements and design of the HA features.


git-svn-id: b6107fd0ee1c9cff0d97bb5f9f4762e9241713e3@4384 0b971d98-bb2f-0410-8247-b05b2b5feb2a

HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j,HuangLS/neo4j