Reorganize the exception handling in exception.h, remove noexcept(false) annotations...

Reorganize the exception handling in exception.h, remove noexcept(false) annotations from the library

 * Provide an AssertNothrow macro that does behave exactly like Assert,
   except that if disable_abort_on_exception was called, it merely prints
   the exception name and continues normally (instead of throwing the
   exception).

 * Use AssertNothrow in ~Subscriptor and ~GrowingVectorMemory to avoid an
   unexpected call to std::terminate in C++11 mode

 * Remove noexcept(false) from the library because this seriously
   inconvenients the user

git-svn-id: https://svn.dealii.org/trunk@31378 0785d39b-7218-0410-832d-ea1e28bc413d