Remove dependency on io.ByteToCharConverter from EditApplicationProperties

EditApplicationProperties uses io.ByteToCharConverter to test whether an encoding is supported.

The class is removed from JDK 1.6-ea, so it looks like it will be removed from JDK1.6.

It is not a good idea to use this class in general as it appears to be Sun JDK specific.

JIRA 3.2.1 (and earlier) will throw the following error when editing General Configuration:

HTTP Status 404 - Could not execute action [EditApplicationProperties]:sun/io/ByteToCharConverter
java.lang.NoClassDefFoundError: sun/io/ByteToCharConverter
at com.atlassian.jira.web.action.admin.EditApplicationProperties.doValidation(EditApplicationProperties.java:106) at webwork.action.ActionSupport.validate(ActionSupport.java:373) at webwork.action.ActionSupport.execute(ActionSupport.java:150) at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:46) at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:131) at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:186) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at