Wrote test for testing code by statement instead of a token list.
Added comparison of statements as strings/tokens.
Refactored compilation unit, moving code into the DiffJ class.
Added comparison of token lists, i.e., statements.

This change continues the migration of comparing statements in their entirety,
as opposed to comparing token-by-token.
Removed unused imports.
Integrated updated Difference class from IJDK Diff.
Continued work on refining differences.

Added test code of statement-by-statement, instead of by token lists.
Removed unused class. Added Tkn, wrapping PMD Token.
Testing of TokenList/Statement diffing code. Incomplete.
Midstream checkin of Code/TokenList to Block/Statement migration.
Additional Code/TokenList to Block/Statement migration.
Added Messages class, for added, changed, and deleted messages.
Removed getCodeTokens from Methods and Ctors.
Further integration of new Messages class.
Further integration of new Messages class.
More migration toward Statements instead of TokenLists.
Further migration from Tokens to Statements.
Integrated Comparable into TokenList.
Moved more diff code away from using Tokens directly.