Add `ReflectAccess` component

This component allows an easy and safe way to access the contents of an
object with reflection.
Add adapter to `INewWizard` for `NewFileWizard`

The `NewFileWizard` interface could not be integrated into the Eclipse
platform. The problem is that various components of Eclipse, namely the
quick access component, the new file menu and the "New" dialog, can only
load entries that implement the `INewWizard` interface. Therefore an
adapter had to be introduced that allows to open the `NewFileWizard`
through the `INewWizard` interface.
Extend fileCreator extension point with description attribute

The description attribute is needed for the quick access component of
Eclipse.
Add registry extension mechanism to codebase

This component is required because it is not always possible to
configure the behavior of the IDE just with XML files.

In the present case, wizard elements defined by the fileCreator extension
point must be added to the platform. Because the fileCreator extension
point is completely independent from the newWizard extension point,
there doesn't seem to be an easier way to hook the additional components
into the platform than by using reflection.

The new `RegistryExtender` component implements this extension behavior.
It is important that this component is called on startup of the Scala
IDE bundle, otherwise it may be loaded to late and some Eclipse
components have already cached some registry entries, which may be
changed by this `RegistryExtender`.
Update shown wizards in Scala perspective

All changes done to a `IPerspectiveFactory` can only be seen when a new
perspective is created, which means that the changes done by this commit
don't have any effects to users that already use the Scala IDE.

Eclipse doesn't seem to support a way to remove and recreate a
perspective when the corresponding bundle is still installed in the
Platform. Therefore users first have to remove the Scala IDE bundle,
then delete the Scala perspective if it is not automatically removed and
finally install the new Scala IDE bundle.
Update `CreateClassProposal` to open `NewFileWizard`
Remove old wizards

They are replaced by the `NewFileWizard`. The only wizard that is kept
is the new project wizard because this one works totally fine.