But they won't do anything useful until the ProcessorGraph is updated

Three important changes:
- The FilterList is now the ProcessorList
- The FilterViewport is now the EditorViewport
- Any classes that need to access important UI objects have become subclasses
  of the "AccessClass". Such objects automatically obtain pointers from
  the UIComponent and register the MessageCenter as an ActionListener. This
  will make it much easier to allocate pointers to objects.

Processors used to have their sample rate and inputs/outputs set when
their source/dest nodes were set. Now, this step doesn't occur until
after the signal chains are constructed. So far, this seems to make
things run much more smoothly.

The LfpDisplayNode/LfpDisplayCanvas are more stable now, although there's
still a bug in the DisplayNode causing small gaps to appear in the buffer.

Because the WiFiOutputEditor also had timerCallback() defined, it wasn't able to
fade in upon creation. This method was modified to solve the problem.

GenericEditors now check their "selected" status before asking to be deleted.

The FilterViewport pauses for 50 ms after deleting a processor in order to
avoid double-deletions.

In combination with an EventNode, a WiFiOutput node is able to send a
simple message to a hard-coded address via UDP. This is the first sink that
actually emits an output. It's obviously over-simplified, but as a
proof-of-concept, it seems to be working well.

Generic Editors colors now match the type of processor.
The FilterViewport layout has been changed to a simple outline.

DataThreads (e.g. IntanThread, FileReaderThread, FPGAThread) are now created at
the same time as the source node, rather than at the start of data acquisition.
New methods for starting/stopping individual threads are required, although
only the appropriate methods for the IntanThread have been written.

Another important change is that the SourceNode now periodically checks for
an appropriate input source every few seconds while acquisition is not in
progress. It's the responsibility of the individual DataThreads to notify
the SourceNode if their input has disappears. In the case of the IntanThread,
this involves attempting to change the baud rate. If an error code returns,
it informs the SourceNode that the input is missing. This, in turn, informs
the FilterViewport that the source is no longer enabled, thus deactivating
that particular signal chain.