Don't register EDynamicPropertyHandler on UI startup for multiple
reasons.

For bug 552372 current code does it too early in the startup sequence -
the workspace location is not defined yet, so a default one will be
instantiated due bundle activation chain triggered by
eFactory.create(eClass).getClass(). This results in either a crash or
wrong (default) workspace used.

The other reason not to activate contributions here is that any
additional bundle activation on UI thread can lead to deadlocks / delay
UI startup.

The two reasons above invalidate the benefit of "eager" startup
optimization proposed in bug 552175.

Change-Id: I947d49864197406722fb0988cd00f77a0a256e00
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>