Database - new nested class Entry

I updated the database class to store Fields
and Strings together as suggested by Mitchel.
The association between the fields and strings
is established by a nested class called Entry.
Database get method change

I split the method get into two separate methods:
 - getAddrByIndex
 - getFieldByIndex
This more clearly documents its intended usage.
FieldSearch change method getEquals

- Renamed the method to findEquals to be
  consistent with the "imagined interface"
  provided by the professor.
- Commented out unimplemented methods
- Changed method to return an arraylist of
  strings.
- Changed method to work with update database class
Merge pull request #2 from cgrycki/master

Updates to Database and FieldSearch