New MetadataAlgorithm, SpikesAlgorithm, and flag-spikes application

Tagging @nshavers @swilbur @bgeels @ahobbs . A brief summary of changes:

• MetadataAlgorithm is a base class that has useful functions for other metadata-type algorithms to inherit from (future Offsets, Gaps, Events, etc.).
• SpikesAlgorithm inherits from MetadataAlgorithm but specifically runs a _despike method and creates spike metadata.
• flag-spikes is an application that runs SpikesAlgorithm and updates/creates spike metadata.
• Flag class has slight changes and new validators, class methods.

A major assumption I make and include validators/functions for is that spike arrays will be contained to 1-day. This way we do not need to worry about overlapping spikes (for now).

I know this needs more work. I still need to:

• Edit _despike to pad edge data with real data like we discussed.
• Edit _despike more, this algorithm works best for 1 kHz data but not necessarily 1 sec data (maybe try wavelets again). I would like to include some pre-processing steps such as identifying spikes by comparing F and DeltaF.
• Look into SNCL codes more for spikes identified at various intervals.
• Clean up code more. What works best for the front-end?