Allow for overriding type and size of an element, opening the path for `int#[]`, `float#[]`, `int#x#`, `float#x#`, `bool#x#`, `vector<type, #>` and `matrix<type, #, #>`. Also allows for specifying the exact type of texture instead of hoping the user gets it right, as well as samplers.
Parameters are also now created if they are invisible, which means that the properties() function must not be called, but they must still be used like any other. This is due to a problem with default values not being applied all the time, and sometimes just vanishing.
The code also now throws exceptions with reasonable text, which should be caught by the gfx::shader implementation and refuse a load of the effect. No other state should be modified at that point, so care must be taken that up until the moment the complete initialization is done no other state is modified.
