This follow the rough pattern of recent *RunConfigurationFactory changes
for build and deploy configurations.

- Collapse the two lines of constructors similar to what
  890c1906

 did for RunConfigurations
  * Deploy* was purely mechanical
  * Build* ctors are split in connects() in the ctor body
    to create "empty shell for clone" etc
    and build step additions in initialize() functions which
    are only used in the create() case.
  -- Allows to collapse the shared 'ctor()' functions, too.

- Move FooBuildConfigurationFactory::create() implementations
  to FooBuildConfiguration() constructor. That was a strange
  and unneeded ping-pong between factories and objects, and
  furthermore allows one level less of indirection (and for a
  later, left out here, some reduction of the
  FooBuildConfiguration interfaces that were only used to
  accommodate the *Factory::create() functions.

- Most {Build,Deploy}Configuration{,Factory} classes had a canHandle(),
  but there wasn't one in the base classses. Have one there.

- Most canHandle() functions were checking simple restrictions on
  e.g. project or target types, specify those by setters in the
  constructors instead and check them in the base canHandle()

- clone() is generally replaced by a creation of a "shell object"
  and a fromMap(source->toMap()), implemented in the base, there
  are two cases left for Android and Qbs that needed(?) some extra
  polish

- generally use canHandle() in base implementation, instead
  of doing that in all Derived::canFoo()

- as a result, canCreate/create/canClone/clone reimplementations
  are not needed anymore, keep the base implementation for
  now (could be inlined into their only users later), but
  de-virtualize them.

- Combine Ios{Preset,DSym}BuildStepFactory. There was only one
  'dsym' build step they could create.

- Split the 'mangled' id into the ProjectConfiguration subtype
  specific constant identifier, and a QString extraId() bit.
  Only maintain the mangled id in saved settings.

- Make ProjectConfiguration::m_id a constant member, adapt
  all constructors of derived classe.

Not done in this patch:

- Finish possible cosmetic changes on top

- Add a way to specify restrictions to supported Qt versions
  (used in Android/Ios), as the base implementation does not
  depend on the qtsupport plugin

- Combine the QList<X> availableFoo() + createFoo(X) function
  pairs to somthing like a direct
   QList<struct { X; std::function<X()>; }> fooCreators()
  to avoid e.g. the baseId.withSuffix() <-> id.suffixAfter(base)
  pingpong

- Remove the *Factories from the global object pool

- Do something about priority(). Falling back to plain
  qmake in android+qmake setup is not helpful.

Change-Id: I2be7d88d554c5aa8b7db8edf5b93278e1ae0112a
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>