The default top-level make rule should only build Mystikos

[mikbras]

Working with Mystikos it time consuming when building from the top level. The default "make" rule builds Mystikos and tests (but not solutions). I propose these rules:

• make -- builds just Mystikos
• make world -- builds Mystikos + tests

The make test rule would implicitly build the tests and then run them.

I tend to type "make" and break out when I see it is building tests, and then I work on my own test.

Also, this is more usable for users who just want to build and install Mystikos (make; make install).