Close #195: Ignore parameters in dependencies (#225)

* Ignore `>`, `<`, `=` and `!` operators, when they are specified in
  the dependencies. This was the desired behavior before, but it was
  not implemented correctly (so it wouldn't ignore them everywhere).
  Of course the real fix would be to honor these operators like apk
  does. But this isn't feasible right now, and it should work for
  most, if not all, our use-cases. I have documented this in the wiki
  under build internals and if we happen to need correct operator
  handling, we should do it then.

Minor other changes:
* `pmbootstrap parse_apkindex`: support optional package parameter to
  only show the parsed content for one package.
* Support building most python APKBUILDs by replacing ${pkgname#py-}
  properly

pmb/helpers/frontend.py

@@ -88,6 +88,11 @@ def parse_apkbuild(args):
 
 def parse_apkindex(args):
     result = pmb.parse.apkindex.parse(args, args.apkindex_path)
+    if args.package:
+        if args.package not in result:
+            raise RuntimeError("Package not found in the APKINDEX: " +
+                               args.package)
+        result = result[args.package]
     print(json.dumps(result, indent=4))