Major refactor / update

[TomDonoghue]

This is a broad set of updates for the whole project, related in particular to consolidating

Broadly, this update includes:

• working through all the current custom code in the repo, and removing as much as can be updated / replaced
• updating code to use the updated / generalized functions from spiketools
• working through & updating all scripts & notebooks with respect to the above
• consolidating analyses on the new core set of analysis, and finishing / extending analyses to be ready to re-run

[claire98han]

@TomDonoghue - Thanks for the update, it's super helpful! left some comments on the scripts, and below are some minor comments on the notebooks. But in general, they all look great!

• 00-DataChecks: tiny typo right before block 18, it should be 'select position only from navigation'
• 02-PlaceCells & 03-SpatialTargetCells: I don't think we need to add a buffer to area_range for the actual analysis, even though it would be helpful to add it for visualization purposes.