Generified FileConverter.

The converter now also checks whether it supports the passed in target type.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/beanutils/branches/java5@1535527 13f79535-47bb-0310-9956-ffa450edef68
Generified StringConverter.

Also added a test class because there was none.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/beanutils/branches/java5@1535528 13f79535-47bb-0310-9956-ffa450edef68