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