Merge pull request #22 from kunki/master

增加四對簡繁轉換，竝刪除一對無效轉換
Rename dictionary_set to DictChain
Rename dictionary_group to DictGroup
Simplify DictChian
Update copyright
Unify interfaces of DictChain
Simplify DictGroup
Simplify Dict
Move dictionary/abstract to src/
Simplify datrie and text dictionary
Update opencc cli tool help text
Reduce ENDIAN
Include stddef.h to remove warnings.
Update gitignore
Refactor and simplify config_reader
Simplify Converter
Add doxygen and rewrite documentation in opencc.h
Rename structs
Update doxygen, readme and gitignore
Update README