Allow to enable meta DEx etc. as build option

Instead of using a define in the header, provide similar behavior as build option.

The main reason for this is automatic testing, whether this is fully operational at this point or not.

It can be used as follows:
```bash
./autogen.sh
./configure --enable-mastercore-development
make
```

---

Upfront: I don't really like it, but I'd prefer it over changing defines in the header.

As alternative I suggest to use a whole new branch, something like "0.0.9-release", which completely removes all parts that should not end up in the release version.

As second alternative this could as well be a startup parameter.