* NftrFont.cs: Basic scheme for importing support

* Program.cs: Tests

* Specification.txt: Need to check some values, not sure about their
  meaning.

* Cglp.cs: Added support for importing

* Cmap.cs: Fix problem not reading last entry for types 1.

* Cwdh.cs: Added support for GlyphWidth importing

* Finf.cs: 

* NitroBlock.cs: Create abstract method check for checking the data of
  the block.

* NitroFile.cs: Added getter for Version. It should call to some
  member to check that the new version is valid for the content
  (downgrading/upgrading)