Get rid of boost dependency for blobby executable

[danielknobe]

We no longer have many boost dependencies. If we can get this dependency removed at least for the blobby application (not for server or test) it will simplify the compilation for various systems.

[ngc92]

In principle, all of our boost dependencies should be easy to handle, since they only depend on the boost headers. So we could just include or git submodule boost, or even use CMake's FetchContent to get the headers.

At the moment, we are using:

• BOOST_THROW_EXCEPTION (probably not really needed)
• shared_array etc. Mostly superceded by std facilities, but note that std::shared_ptr<T[]> is a C++17 addition.
• crc
• string algorithms

[danielknobe]

It should be a rule for now to use header only boost components. This makes the whole multiplatform build easier.

[ngc92]

This suggestion, to me, makes much more sense than to avoid boost in its entirety. IMO it's just too useful for that :)