Xpart

**Changes:**
- Random number generator can generate Gaussian distribution.
- Setters for energy variables do not change lost particles nor those for which np.nan is provided.
- build_particles and and generate_matched_gaussian_bunch work correctly with pyheatail interface enabled
- Fix in Particles.hide_lost_particles

**Changes:**
- Tolerances for one-turn matrix validity checks can be modified at runtime
- Other small fixes

**New feature:**
- Match particle distribution at an arbitrary location in the ring.

**Fix:**
- Fix problem with xpart.Particles.to_dict when PyHEADTAIL interface is enabled

**Changes:**
- Disabled automatic symplectification of one-turn matrix (found to degrade accuracy on vertical dispersion).
- Changed algorithm for LocalParticle_add_to_energy.
- Moved linear_normal_form module from xpart to xtrack (aliases still present in xpart for now).
- Introduced check on keyword arguments of Particles constructor (an exception is raised if invalid names, e.g. typos, are present).
- Removed double underscore from random number generator state variables.

**New feature:**
- Use linear matching when bunch is much shorter than RF period