Additional Handling for ALTER TABLE statements

* Added a function to detect if an index exists on a table
* Added a function to detect if a column exists on a table
* Created a parser to handle ALTER TABLE statements
 * The table name will be checked (exception written if needed)
 * The table name will have the prefix added (if needed)
 * Columns and Indexes which already exist will not be added
Added some additional "checks" for other potential ALTER TABLE table_name ADD * statements.
Additional sanity checks before checking for the existance of a column or index on a table.
Merge pull request #45 from lhungil/update-sql-alter-table

Additional Handling for ALTER TABLE statements