oneof support in muspec

Oneof groups can now be defined in the µSpecs.

fieldname: '* string:2 = default value [oneofname] #The description.'
!_______!  !_!!____!!_!!______________!!__________!!________________!
    |       |    |   |          |            |              |   
    |       |    |   |          |   oneof definition in []  |
    |       |    |   |    default value (=)                 |
    |       |    |   |                                      |
    |       |    |   |        description (recomended) begins with a #
 field name |    |   |   
            |    |  field id, indicated by a :   
            |    |  
            |   type  
            |     
       Indicator for required (*), readonly (-), repeated ([])

Attention:

The default values are synced correctly now.
If you work with µSpecs and use default values, you have sync back the default values from the spec once. Do this by runningfuro spec2muSpec.