add clear icon to resource bundle

Author: PhilippSalvisberg

sqldev/src/main/resources/org/utplsql/sqldev/resources/UtplsqlResources.properties

@@ -17,6 +17,7 @@ INFO_ICON=/org/utplsql/sqldev/resources/images/info.png
 REFRESH_ICON=/org/utplsql/sqldev/resources/images/refresh.png
 RUN_ICON=/org/utplsql/sqldev/resources/images/run.png
 RUN_WORKSHEET_ICON=/org/utplsql/sqldev/resources/images/run_worksheet.png
+CLEAR_ICON=/org/utplsql/sqldev/resources/images/clear.png
 
 # Translatable text
 PREF_LABEL=utPLSQL