Fixed rtslib version require for debian
Migrate running config if no startup file

This allows to ease a little bit migration from development setups and legacy
lio-utils based installations. Configuration dumps only happens when starting
/etc/init.d/target if there is not pre-existing /etc/scsi_target.lio config and
the configfs target node is up.

* Initscript start detects migrations and saves running config
* Added lio-utils migration information in README.md
Cleaned up commented code in ui_command_configure
saveconfig now uses same logic as config mode commit

* Moved the configuration backup and dump logic to a separate class method:
  CliConfig.save_running_config()
* Using in both config mode commit and legacy mode saveconfig
Makefile clean target rm's all *.pyc *.swp files
Remove module loading logic, reply on initscript
Use FabricModules.all(), not RTSRoot in initscript

* In rtslib/61f72fd404eda5e263c2fd774db814dde5daa7cf, all module loading
  logic was removed from rtslib, and thus RTSRoot cannot be instanciated
  before the initscript loaded the target module.
* FabricModules.all() is a class method that only relies on specfiles
Initscript stop action LSB compliance fix

When trying to stop an already stopped service, the initscript should succeed
and return 0. We now return 0 when trying to stop the target when
/sys/kernel/config/target does not exists. This also fixes a potential problem
when upgrading targetcli with the target stopped.
Initscript rely on rtslib to create configfs nodes

We used to mkdir the fabric modules configfs nodes after loading the kernel
modules. RTSLib does this already, so rely on it and remove that code from the
initscript.
Use parse_specfile(), list_specfiles() in initscript

Following rtslib/4f735bb86e8cef3de111d4ddff98695aeb35536e, we cannot use
RTSRoot.fabric_modules before loading the kernel modules.

To circumvent the problem, rtslib/93934a720968780b24ce03bb8e03d81f352d6662
introduced parse_specfile() and list_specfiles() which only require the
specfiles to be present on the system.
Use RTSRoot.fabric_modules, not loaded_fabric_modules

RTSRoot now exposes only loaded modules and has no loaded_fabric_modules
property anymore, c.f. rtslib/a4930ad0b4beaa4a7b10e7e8f9389e618245fd60
Initscripts start warns of already loaded modules
Makefile: VERSION uses "~" for "-" in git tags

* This makes for better version comparison in distributions.
  In Debian, 3.0~rc1 < 3.0 < 3.0-rc1.
* Added version target to display computed version string
* Use the same variable for rpm and deb changelogs