Part masses

this PR resolves #456.

    It adds to PART

:MASS
:DRYMASS
:WETMASS
:HASPHYSICS //this was important to the calculation so i decided to expose it

    It adds to SHIP

:DRYMASS
:WETMASS
:TYPE //should have be a different PR but i got carried away

You should now be able to change craft names and types in kerboscript.

    
IMO, PartValue should also have a DRYMASS/WETMASS suffix on it just like vessel does, to make use of these utilities.  But that can be part of a separate issue.