This commit replaces the custom implementation of the sort.Reverse
function with golang's built in sort.Reverse function to reverse the
order of the migration scripts (descending sort). In the EnsureDbVersion
function it simplifies logic paths by reducing the number of conditions
checked before a new version is added to the "to skip" slice. In
function splitSQLStatements it changes the order of the conditions
checked because 1) It is not possible for statementEnded to be true and
ignoreSemicolons to be true at the same time because those variables are
set together in the same block and 2) ignoreSemicolons belongs together
with endsWithSemicolon line.
Also renamed script variable to scriptFile variable to indicate
scriptFile is a path, not a script in a string variable.