Add new interface wizard

Classes and resources for the new interface wizard are added. Moreover,
'pl.edu.mimuw.nesc.wizards.fields' package is created for simpler
implementation of subsequent wizards.
Add implementation of the header file wizard

Wizard that allows creating header files is added together with an icon for
it. 'pl.edu.mimuw.nesc.wizards.fields' package is enriched with a WizardField
subclass that allows entering a file name.