Refactor the Type and Value systems, cleanup code, add useful macros, documentation...

Refactor the Type and Value systems, cleanup code, add useful macros, documentation, etc..
* Add struct GetTypeImpl and its specializations in type.h.
* Make GetType() an inline function that uses GetTypeImpl internally.
* Add basic documentation for Type, GetType and their associated macros.
* Add QGLIB_STATIC_ASSERT() macro to allow specifying a nice assertion message when using C++0x.
* Add macros for defining ValueImpl specializations.
* Remove the ValueBase::getFoo / ValueBase::setFoo methods.
* Place all basic ValueImpl specializations in value.h, remove the valueimpl headers.
* Remove VALUE_ASSERT and use a type check inside ValueBase::get/set.
* Remove ValueImpl specialization for pointers. Allow only void* (Type::Pointer) and const char* (Type::String).
* Register Type, ValueBase, Value, SharedValue, StructureBase and SharedStructure with the type system.
* Attempt to fix the mess with the included headers. Try to include all used headers instead of relying on indirect inclusion from global.h.
* Remove the peekGValue() methods from ValueBase and replace them with operator GValue*().
* Minor fixes here and there...

(Long commit, sorry...)