ENH: improvements related to interface of tracking functions.

 - improve docstring of line_pass and ring_pass functions;
  - fill lost_element and lost_turn with -1 for particles that were not lost;
 - lost_flag is now a list of booleans for each particle;
 - change order of arguments in element_pass, line_pass and ring_pass so that they are sorted by constant inputs, changing inputs and pure outputs;
 - create separated method to check if particle was lost;
 - in python interface: fill numpy array of initial tracking coordinates with the coordinates at the point where particles were lost. For surviving particles, nans are used.

Author: fernandohds564

include/trackcpp/dynap.h

@@ -27,8 +27,8 @@
 struct DynApGridPoint {
   Pos<double>  p;              // Dislocation around closed-orbit
   unsigned int start_element;
-  unsigned int lost_turn;
-  unsigned int lost_element;
+  int lost_turn;
+  int lost_element;
   Plane::type  lost_plane;     // Plane::no_plane,Plane::x,Plane::y,Plane::z
   double       nux1, nuy1;     // tunes at first half number of turns
   double       nux2, nuy2;     // tunes at second half number of turns