Flare 1.l.0 new features and bug fixes

* New features:
  - Redundant index servers
  - Add coordinator classes to store and restore the state of the index server
    - Add coordinator class for handling the state of the index server
    - Move the code for storing and restoring flare.xml from cluster to file_coordinator
    - Add zookeeper_coordinator class to store flare.xml into a zookeeper cluster
    - Add --index-db option to flarei to specify a database for storing flare.xml
    - Add --index-servers option to flared to specify multiple index servers
    - Add connect_retry_limit parameter to connection_tcp to avoid retrying too much in open()
  - Improved statistics information
  - Automatically node down when storage error happens

* Bug fixes:
  - Modified include guards to fit them to the C++ standard naming convention.
  - Remove unnecessary null check and avoid double free
ready for 1.1.0
Merge branch 'master' of github.com:gree/flare