Materialsation: Create materialisation script from the scratch

[michael-barth-elco]

We have many prerequisites for the materialisation used for the plugins before, but for the easy materialsation we duplicate them. This are the target platform, the Eclipse SDK and the artefact publication of the build artefacts. This enhancement get acces to this configurations and create the build.properties file needed for the materialisation (and other files if necessary) and calls the pde build with the existing Eclipse SDK.

[jotdl]

I already did a lot of work visible in the materialisation branch. This is basically a partial port of tycho to gradle.
It's not pretty at the moment but shows how P2 can be used "directly" in gradle. Therefore it was necessary to embed an equinox runtime into gradle and use it to execute certain tasks.

What's left is that we would need to adapt tychos logic to extend a given product by executables. This should be (hopefully) enough to materialise a full working RCP application in the workbench.

Due I am quite busy at the moment (finishing my studies) I would appreciate any help and input!