Fixes and additions:
* Fixed split in FileParser.creaPlan because Windows hates '¬'
* Changed io constants order
* Fixed buscarAsignaturaPorCod NullPointerException
* Added JPopupMenu to AsignPanel 
* Fixed AsignaturaEditor defaulingt matriculada to false, it now defaults to a.isMatriculada
* Added getPeriodo() to PeriodPanel 
* Changed gui.mainframe order of appereance, to implement in the future a loader...