The global property FeatureSummary_<TYPE>_DESCRIPTION can be defined for
each type to replace the type name with the specified string whenever
the package type is used in an output string.
These new global properties were added:
* FeatureSummary_PKG_TYPES: Package types accepted by FeatureSummary
(default REQUIRED RECOMMENDED OPTIONAL RUNTIME).
* FeatureSummary_REQUIRED_PKG_TYPES: Package types that will cause
FeatureSummary to abort when called with
FATAL_ON_MISSING_REQUIRED_PACKAGES and a package in these categories
is missing (default REQUIRED).
* FeatureSummary_DEFAULT_PKG_TYPE: Default package type assigned when
not explicitly assigned by the user (default OPTIONAL).
This allows to add and remove new package types that can be printed
selectively using the "WHAT" argument.
If a feature is added multiple times via ADD_FEATURE_INFO it should
appear only once in FEATURE_SUMMARY.
Signed-off-by: Gregor Jasny <gjasny@googlemail.com>