Moved endlog and snapshots into separate files. Closes #11.
Merge branch 'master' of https://github.com/wschreyer/PENTrack

Fetching updates from Upstream copy.
Fixed bugs in neutron total energy calculation.
Code cleanup
Moved NR3 independent code into separate compilation units.
Improved precision of kinetic energy calculation
by using higher order series expansion of relativistic gamma factor at
lower velocities.
Improved compatibility with older compilers
Added checks if log files could be opened.
Merge branch 'master' of https://github.com/wschreyer/PENTrack

Reverting to Upstream Copy to remove recent errors with Segmentation Fault.