Add a type class for the property of being forthcoming

This type class captures those objects where it is meaningful
to ask if the object presented to us is forthcoming.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
Also generate a predicate for being forthcoming

As we generate forthcoming objects with template Haskell
anyway, also generate the a predicate indicating if an
object is forthcoming.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
Instance Disks as ForthcomingObject

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
Instance instances as ForthcomingObject

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
Add field list for the property of being forthcoming

With the introduction of forthcoming objects we also want
to support queries for the property of being forthcoming.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
Support queries for the forthcoming bit of instances

As instances can now be forthcoming, allow queries for that
property as well.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>
htools Luxi backend: query forthcoming flag

As forthcoming instances need to be handled differently
by htools than real ones, also query that bit via the
Luxi interface.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Petr Pudlak <pudlak@google.com>