Changes:

1. equities and securities list aren't completely reloaded at each database change,
2. displayed columns are selectable,
3. no crash after deleting first equity (corner case),
4. no crash after deleting equity in accounts view and then switching to investment view,
5. context menu in equities tree updates properly when clicked on columns other than name,
6. Call KMyMoneyApp::slotUpdateActions once instead of four times when selecting equity,

Creating, deleting, editing equity in accounts and investments view.
Modifying security in securities tab.
Buying shares in ledger.