boost: drop dependency on is_fundamental in serialization

There's only one case where a vector containing a fundamental type is
serialized all-at-once, unsigned char. Anything else would lead to
strange results.

Use a dummy argument to overload in that case.
boost: drop dependency on tuple in serialization

There's only one user of this form of serialization, so it can be easily
dropped. It could be re-added if desired when we switch to c++11.
boost: remove CPrivKey dependency from CECKey

This allows CECKey to be used without directly depending on the secure
allocators
boost: drop boost dependency in core.cpp
boost: drop boost dependency in utilstrencodings.cpp
boost: drop boost dependency in version.cpp.

Also add a test to verify.