Browsing German translation

Macros to help dealing with required options.
VSH_REQUIRE_OPTION_EXPR:
*
* @NAME1: String containing the name of the option.
* @EXPR1: Expression to validate the variable (boolean variable).
* @NAME2: String containing the name of required option.
* @EXPR2: Expression to validate the variable (boolean variable).
*
* Check if required command options in virsh was set.  Use the
* provided expression to check the variables.
*
* This helper does an early return and therefore it has to be called
* before anything that would require cleanup.