Reworking/cleaning rpm build target.
Commands via variables instead of hard coded.
Reworked project to project dependency check code.

 * Removed api-level requirement constraint, did not work. Currently only
   availabilty of requirement is checked for. I.e. if foo requires bar it does
   not matter if bar is of version 1.0 or 2.0. Foo only wants A bar.
Cleaning up common macros file.

 * Removed buildinfo target, not a macro.
 * Reworked NVR-tuple handling macros, some removed, some added.
Reworked bobshell target and added buildinfo target to helpers file.
Added git whatchanged to buildinfo.txt content.
Repaired broken target .d-files inclusion... (when did this break?)
Textual changes only...
Renaming internal variables, dot-schema is nicer.
Removed check of variable DEFINES

 * Nice to have, but have less code is nicer. Better to have rules stating
   that reassigning variables is not allowed. Besides, the use have been none
   or very little. If the need reappers a better solution could be
   implemented.
Added handling of build architecture, only i686 and x86_64 at the moment.
New naming schema for commands, __bob.cmd.*
Renaming variables related to files.
Removed unused variables.

 * Are always empty and cannot be used externally.
Added feature for implicit source definition.
Textual changes only...
Removed fairly unused version target.
More verbose remove target for specfile.
Added README file (as prompted to by GitHub).
Documentation file (asciidoc syntax).