Add package generator script

- add a 'pckgen' script to generate various OpenCAS packages like
release archives (tar, zip), RPMs (source and binary) as well as to
create version file with metadata
- add a SPEC file for RPM creation
- add Makefile targets to use 'pckgen' script through 'make <package>'

'pckgen' script has a bunch of features for package generation.
Read './pckgen --help' for more information on usage scenarios.

Script is also prepared to easily add new packages creation in the future.

Signed-off-by: Rafal Stefanowski <rafal.stefanowski@intel.com>

Makefile

@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: BSD-3-Clause-Clear
 #
 
+PWD:=$(shell pwd)
+
 default: all
 
 DIRS:=modules casadm utils
@@ -12,4 +14,19 @@ DIRS:=modules casadm utils
 all $(MAKECMDGOALS): $(DIRS)
 
 $(DIRS):
+ifneq ($(MAKECMDGOALS),archives)
+ifneq ($(MAKECMDGOALS),rpm)
+ifneq ($(MAKECMDGOALS),srpm)
 	cd $@ && $(MAKE) $(MAKECMDGOALS)
+endif
+endif
+endif
+
+archives:
+	@utils/pckgen $(PWD) tar zip
+
+rpm:
+	@utils/pckgen $(PWD) rpm
+
+srpm:
+	@utils/pckgen $(PWD) srpm