allow to specify versions with zypper (#2328)
allow to specify versions with zypper (#2328)

* fixes #2158
* handles version-specifiers (>,<,>=,<=,=) correctly
* adds option "oldpackage", which is passed to zypper
  * this is implied as soon as a version is specified
  * it can be used independently to allow downgrades coming from repos
* add __main__ check
* extend documentation on version specifier

thaim/ansible,thaim/ansible