Remove default allocator for estell exceptions

[kammce]

Currently we allocate 256 bytes for a single exception to be thrown in a single core system. This is useful for developers but has a cost of losing a bit more than 256 bytes of memory.

New behavior

• Keep a statically allocated polymorphic allocator (should be the cost of a pointer)
• The application is forced to set an exception allocator prior to using anything that can throw an exception
• If an exception is thrown without an allocator set, then the application terminates.
• The set_exception_allocator() will allocate and deallocate an instance of std::bad_alloc to verify that the allocator can at least allocate std::bad_alloc object. The assumption will be that the allocator can at least allocate std::bad_alloc.
• If the exception allocator has completely exhausted and is unable to allocate a bad alloc object, then the application terminates.

Another option other than terminating the application would be to have some reserve memory for std::bad_alloc, but this has a per-thread cost that I think is unreasonable for many applications. So termination seems like the proper action if error reporting fails.

[kammce]

We should remove the set_exception_allocator and get_exception_allocator and replace these with weakly defined implementations that can be overriden. Like operator new()