changed tinyxml2 - can add xml header now, #11
saved simulation has correct XML structure, closes #11
little assertion in test-core main and in Simulator
LoggedException class first impl, for #16

Additionally Logger has functions:
throwIfFalse(bool, const char*)
throwIfTrue(bool, const char*)
for convenient checking, logging and throwing all-in-one
UnloggedException added, for #16
core:: functions throw only(Un)LoggedExceptions, closes #16
Enhanced descriptions in SimComponents about exceptions, #16
exceptions documented, added some checks, little fixes, #16

Exceptions are specifically mentioned in header comment,
if thrown.

Some additional null-checks-throws added for completeness,
and (Un)LoggedException::operator= fixed
Merge pull request #19 from rideofyourlife/core-project

Core project - Exceptions standarized and XML are well-formatted