[Mono] Preferences dialog: fix enabling of Upload Type radio buttons (WebGenTypePanel)

Upload Type radio buttons (WebGenTypePanel) should be enabled whenever
Web Generation check box (GenerateWeb) is enabled, not when FTP radio
button (FtpModeEnabled) is enabled.

Move enabling of WebGenTypePanel to appropriate case in the switch block.
[Mono] Work around Preferences dialog's controls issues when closing child windows.

Investigation credit goes to Stephen Gordon <firedfly@gmail.com>.

Whenever Preferences dialog creates child windows (message boxes,
file/directory dialogs etc.), Mono runtime disables all the controls
in the Preferences dialog.

Incidentally, this 'automatic' control disabling process fires all
all usual control events which (due to binding) cause changes to
associated tab properties which, subsequently, fire PropertyChanged
events.

This creates a problem as now we have two entities disabling the controls:
(a) Mono's 'automated' control disabling
(b) Handle*PropertyChangedForMono

Now, as controls are being disabled, Handle*PropertyChangedForMono
handlers typically disable all dependent controls.

This interferes with Mono's process (presumably, Mono is able to tell who
disabled given control last and doesn't re-enable controls it didn't disable
in the first place) and, effectively, some controls are not getting
re-enabled when child window closes.

Work around the issue by having Handle*PropertyChangedForMono perform
no actions unless PreferencesDialog is enabled.