Show additionnal information on TableEditor column info tool
Draw Key icon on key column
Read primary key of table
Add Javadoc [skip ci]
Javadoc
Fix method name and javadoc
Merge pull request #652 from nicolas-f/feature/H2ConstraintShow

More details on Table Editor column information.

If the column has a primary key, the new class TableEditorHeaderRenderer will show a key icon next to the column label.
More information is retrieved from JDBC on column.
About #651