Merge pull request #5 from k-hotta/master

a pull request at 130801
create a class for a source file
create a class for a source file
create a file table in db
modify classes related to ast parser to use FileData instead of file paths
[REFACTORING] move registerers into another package
create a class to register files into db
create an abstract class to retrieve elements from a given db
implement a function to retrieve revisions from db
implement a function to retrieve files from db
create a constructor for retrieved instances
change the type of the field in MethodData that has VectorData from VectorData to long (id of VectorData)
change the type of methods from List to Map
tailor analyzers for files to match the structure change in previous commits
implement a function to retrieve methods from db
remove retrieveInSpecifiedRevision from AbstractElementRetriever
remove an unused method from AbstractElementRetriever.java
implement a function to retrieve vector data
change registerers to set the field of db connection with the specified instances
change retrievers to set the field of db connection with the specified instances