#8 Add EQUALS that outputs = operator or IS NULL if parameter exists but is null, added same functionality to LIKE
#8 Created OperatorSqlFragment as baseclass for Like and Equals
#8 Added copyright statement to EqualsSqlFragment and OperatorSqlFragment
Merge pull request #9 from andrewdmay/issue-8-null-param

Add @EQUALS that generates = or IS NULL

Fixes #8