Update contracts.rst
Update contracts.rst

I left the example with contract C only, showing the access specifiers discussed at 186-188. The specifier of data is left public since nothing is related to accessor functions now.

Added a separate example with contracts C, D and E to show specifier's effect. 

Added a separate example to prove the synthesizing of accessor functions.

Added a new example to show the internal/external call of the accessor, according to existent discussion.
ruchevits/solidity,ruchevits/solidity,ruchevits/solidity,ruchevits/solidity