PPMS measurement plugin

[aalbino2]

Some doubts to ask:

• Is there a max number of samples that can be loaded?
• full set of sample possible keys is required to build a complete class.
• explain the following part of the header:

  
  STARTUPAXIS, X, 2, LINEAR, AUTO
  STARTUPAXIS, Y1, 7, LINEAR, AUTO
  STARTUPAXIS, Y2, 9, LINEAR, AUTO
  STARTUPAXIS, Y3, 27, LINEAR, AUTO
  STARTUPAXIS, Y4, 29, LINEAR, AUTO
  TIMEMODE, SECONDS, RELATIVE
  PLOT_APPEARANCE, ALL, HORZ_GRID_ON, VERT_GRID_ON,,AUTO_LINES
  RECORDS, ALL_RECORDS
  DATATYPE, COMMENT, 1```