Make Transfer Options page easier to use and understand

[Enet4]

The current Transfer Options page leaves a bit to be desired. The "Select All" and "Deselect All" will check and uncheck all transfer syntaxes for all SOP classes. It is a heavy operation which the user might not predict, since the page only presents checkboxes for the SOP class currently selected. Other than this button, transfer syntaxes need to be unchecked one by one, with no extra facilities for disabling or enabling only baseline transfer syntaxes (Implicit VR Little Endian and Explicit VR Little Endian).

I propose that these aspects are improved:

• There isn't a way to enable a transfer syntax regardless of the SOP class (or at least for those already admitting at least one transfer syntax). This means that allowing a transfer syntax requires looking up every applicable SOP class.
• This could be disambiguated by adding another set of buttons to enable all transfer syntaxes for the visible SOP class.