CP-5750: Code tidy. Comment improvement.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Changed the declaration for the ActionBase events Completed, Changed and
NewAction to use the Action<ActionBase> delegate instead of EventHandler. Thus
there is no need to fire them with Empty or null EventArgs and on several occasions
we avoid casting objects in the event handlers.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: When a License warning is generated, create an alert rather than an Action.
Removed ActionType.Alert. Removed Alerts checkbox from the Log tab.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Removed ActionType; the actions should be categorised by status (in progress,
succeeded, failed; cancelled at the moment counts as failed, we may need to distinguish
in future). As a consequence the filter checkboxes from the top of the Log tab
were removed and some temporary changes were made to the drawing of action rows
(the controls will change completely in a subsequent commit).

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Removed Clear button. Initial implementation of top ToolStrip and
DismissAll/DismissSelected split button.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Do not filter the Log tab entries according to the selection on the treeview.
For the time being show all entries. New filtering according to the entry location
will be implemented in a future commit.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Initial implementation of the new Events DataGridView.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
Removed unused methods.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
Code efficiency: compacted methods retrieving IXenObjects from VirtualTreeNodes
because certain checks were run more than once.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Implemented ability to sort events. Set vertical scrollbars for the gridview.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Implemented event filtering by status, location and date.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Moved capping of event numbers to a more relevant place and corrected logic
to remove the oldest items first and fire an event when doing so.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>
CP-5750: Added label to indicate when filters are on/off. Changed the order of
the items on the actions split button.

Signed-off-by: Konstantina Chremmou <konstantina.chremmou@citrix.com>