Everything what was in src/ is now in src/Corrade, everything from
src/Plugins is now in src/MagnumPlugins, everything from external/ is in
src/MagnumExternal. Added new CMakeLists.txt file and updated the other
ones for the moves, no other change was made. If MAGNUM_BUILD_DEPRECATED
is set, everything compiles and installs like previously except for the
plugins, which are now in MagnumPlugins and not in Magnum/Plugins.
* They are now deinlined into source files, as most of the classes have
either heavy members (std::vector) or virtual methods.
* All of them are explicit now (that should be already done, don't know
why not).
* Passing huge classes by value and using move constructors to avoid
unnecessary copying.
SizeTraits class provides suitable types for given data size at compile
time, SizeBasedCall can call suitable templated overload based on given
data size at runtime.
Also added meta classes Pow and Log for computing powers and logarithms
at compile time, usable mainly in conjunction with SizeTraits. Their
implementation is checked at compile-time using static_cast().