Improvements in key visualization and bugfix

.../inaf/oats/ia2/tapschemamanager/businesslayer/Column.java

.../inaf/oats/ia2/tapschemamanager/businesslayer/Schema.java

...t/inaf/oats/ia2/tapschemamanager/businesslayer/Table.java

...af/oats/ia2/tapschemamanager/businesslayer/TapSchema.java

...it/inaf/oats/ia2/tapschemamanager/businesslayer/Util.java

...s/ia2/tapschemamanager/webapp/EditTapSchemaPageModel.java

TapSchemaManager/src/main/webapp/css/fontello.css

TapSchemaManager/src/main/webapp/editTapSchema.jsp

TapSchemaManager/src/main/webapp/fonts/fontello.eot

TapSchemaManager/src/main/webapp/fonts/fontello.svg

TapSchemaManager/src/main/webapp/fonts/fontello.ttf

TapSchemaManager/src/main/webapp/fonts/fontello.woff

TapSchemaManager/src/main/webapp/js/edit-tapschema.js

...naf/oats/ia2/tapschemamanager/datalayer/DataProvider.java

...t/inaf/oats/ia2/tapschemamanager/datalayer/KeyEntity.java

...naf/oats/ia2/tapschemamanager/datalayer/SchemaEntity.java

...inaf/oats/ia2/tapschemamanager/datalayer/TableEntity.java

...oats/ia2/tapschemamanager/datalayer/TapSchemaHandler.java

TapSchemaManagerDL/src/test/java/TestQuery.java