trajectory split and join + minor improvements in logging

New functionality

• curve module:
  • Added functionality to split and join Splines and Trajectories (preserves original shape)

Improvements

• curve module:
  • increased tolerance for segmentation errors in Spline and QuaternionSpline classes (now uses global variable to define tolerance)
• io module:
  • LogFile now has a flag to enable/disable skipping of passed LogFileData objects
  • LogFileData now creates a default column header from specified column names
  • Logger: improved closing procedure for LogFile objects in list (now checks, if file is open and tries to write footer)
• Eigen: updated to version 3.3.7
• Style: removed grouping of includes

Bug fixes

• CircularBuffer: fixed bug which occures when the user specifies a zero buffer size (now minimum 1 element is in the buffer)