Generic changes:

- Genuinely unused variables (-Wunused-variable): delete
  them. Sometimes add a comment if the variable is for an extension of
  the code that isn't done yet.

- Variables that became unused due to commented-out
  code (-Wunused-variable): comment out their definitions. Dirty, but
  that's because commenting out code instead of deleting it is
  dirty.

  Many of these are due to commented-out printlines that should have
  been log messages that only get emitted at high verbosity level.

Specific changes:

- SpikeObject.cpp (-Wunused-value): move initialization of loop
  variable into first for loop clause to silence the warning.

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

Rearrange member initialization in constructors to silence GCC
-Wreorder warnings (-Wreorder is enabled by -Wall).

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

If continuous channels are toggled for recording within their respective editors,
a "writeContinuousBuffer" function will be activated within the RecordNode. This
function doesn't do anything yet, but it will make it easy to add diskwriting
capabilities in the near future. Once a stable format for events has been established,
a similar function will be implemented for writing event buffers to disk.

The EditorViewport now contains buttons to scroll through multiple tabs,
or scroll across long signal chains. Now, there can be infinitely
many signal chains of infinite length (if you have a lot of time
on your hands).

Functions for managing the signal chain are no longer handled by
the EditorViewport, but by the SignalChainManager