Make the order of viewers configurable inside ini for each plugin type

[rzaharia]

Each type plugin should be able to have a configurable way of noting the order of viewers that are available

Consider the following scenario: By default the plugin PE, opens first BufferViewer and the second one is DissasmViewer. Using some configuration,for example:

[PE]
viewers = [DissasmViewer, BufferViewer]

Then it should open first the DissasmViewer and then the BufferViewer