First application work added.

construct a application simulating some moving sphere
framework &requirement see README.md
Readme fixed

markdown language fixed;
remove hgih-dimonsion system requirement.
add basic element defination

*coordinate with operator overloading
*point
*area
*mass point
*charge point
*gravity field
*e&m field
add .cpp

*fix class defination problem
*fix operator overloading name
*add .cpp
*done point class function
a lot of problems fixed

aha
Merge pull request #1 from frequencyhz/master

input from H.Z with latest class