At this stage the following is implemented:
* Mvn class and schema to load and validate MVNX files
* Plotter base class with functionality to host multiple plots and multiple lines per plot
* Interaction: custom buttons and text prompts
* Two specific subclasses of the plotter: one for editing and one for checking signals. Subclasses extract the acceleration magnitude for both arms from the MVN by default.
* Editing class has functionality to provide 4 anchor points and export synched MVNX