Upgrade docs and config file

[jefftlin]

What is the purpose of the change

(For example: Exchangis-Job defines the core ability of Exchangis, it provides the abilities of job management, job transform, and job launch.
Related issues: #50. )

Brief change log

(for example:)

• Upgrade reademe;
• Rename config file from exchangis-server.properties to dss-exchangis-server.properties;
• Upgrade some docs.

Verifying this change

(Please pick either of the following options)
This change is a trivial rework / code cleanup without any test coverage.
(or)
This change is already covered by existing tests, such as (please describe tests).
(or)
This change added tests and can be verified as follows:
(example:)

• Added tests for creating and execute the Exchangis jobs and verify the availability of different Exchangis Job, such as sqoop job, datax job.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• Anything that affects deployment: (yes)
• The Core framework, i.e., JobManager, Server.: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)