Instead of the dependency oriented logic, switch to print them
for each package or name needed. Might give a bit more readable
errors now. There's still few corner cases that proper error is
not output, which are cought by the test cases.

Implementing basic dependency handling, install_if and awareness
of pinning.

also merge the expected output to the *.test files.

 * the solver no longer does look-ahead locking of names
   (could be possibly optimized later); instead names are now
   always ordered strictly to properly detect the package names
   which are unsolveable
 * basic error tests added, so we can see the most likely problem
   in dependencies easily