Patch-gen tool should provide users with better error messages

Patch-gen tool should provide better error messages to user. Eg. telling what exactly is wrong, instead of listing the full usage.

[vtunka@voidray tool]$ ./tool.sh --create-template --cumlative 6.2.0
USAGE:
patch-gen.sh --create-template --one-of [patch-id]
patch-gen.sh --create-template --cumulative [patch-id]
this will create a patch-config-[patch-id].xml
if this is not desired just append --std.out

There is a typo in --cumlative instead of --cumulative, but the tool doesn't say that, and user is left to explore possible sources of error.