make frames manditory

[cpiker]

The vecClass attribute of element <vector> is not parsed in the serialization module, for good reason. The <frame> element defines the vector class.

Right now the stream XSD schema allows for undefined frames to be created by adhoc by vector variables without a formal frame definition. When they do it's split between the dimension level and variable level which can lead to inconsistent results.

If frames definition were mandatory, vecClass would not be needed and frame names could be moved to the variable elements.