Add org.scalaide.ui.wizards.fileCreator extension point
Add new "New File Wizard"

For more information about this wizard see the proposal that can be
found in the associated ticket.

Fixes #1002103
Add combo box that can show images

The implementation is copied from the nebula project. A link to the
source and some examples can be found in the copyright comment of the
code.
Validating logic now checks Scala and Java keywords

Previously it was only checked if identifiers can not correspond with
Java identifiers which is not enough for Scala identifiers.

Furthermore package names are not allowed to contain Java identifiers.
The Eclipse package hierarchy view can't display them correctly and even
the Java compiler of JDT seems to have problems with them.
Create first file creator for the new file wizard
Add file creator for traits
Add file creator for objects
Add file creator for package objects
Show error messages for package objects on wizard creation

The default behavior was that no error messages are shown at wizard
creation. For package objects this behavior is not the most useful one
because it can be that the initial path is already valid. In case it is
not users show be notified about this immediately.
Add file creator for apps (classes that extends the trait App)
Add selection listener to combo box in new file wizard

Without the selection listener there does no validation of the file name
happen when users change the type of the new file with the mouse instead
of the keyboard.