cli: Catch xmlrpc exceptions during login/logout

* bugz/cli.py: Add try/except parts around xmlrpc calls
PrettyBugz: Better handle exit values.

* bin/bugz: main(): Use return statement rather then sys.exit()
* lbugz: Distribute exit value out to shell.
cli: Reorganize error handling

* bin/bugz: Consistently format errors.
* bugz/cli.py: Parse config file locally.
* bugz/errhandling.py: New file, extract BugzError due to include loop
log: added interface for logging

* bugz/log.py: New file.
log: add possibility to setup verboseness of debug

* bugz/log.py: Add 'verboseness' param to log_debug()
log: move to default logger

* bin/bugz: Move to new logging hierarchy.
configfile.py: Add hierarchical configuration parser

This is not working revision.

* bugz/configfile.py: Add several methods.
config: Use the /etc/pybugz/pybugz.conf as default config

* bugz/cli.py: Define DEFAULT_CONFIG_FILE
* bugz/configfile.py: Rename to 'discover_configs'
configfile.py: Code cleanup

* bugz/configfile.py: Code cleanup, simplification of some parts.
config: Add default configuration files

* conf/conf.d/gentoo.conf: New file.
* conf/conf.d/redhat.conf: New file.
* conf/pybugz.conf: New file.
config: Change the semantics of configuration a little

The 'settings' section does not need to be called settings now.  It just
requires adding the 'type = settings' option inside.

The 'default' section is now not a section anymore — it is a concrete item
in settins: 'default = DefaultConnection'

* bugz/configfile.py: Change semantics.
bugz/log.py: Add 'I' section inside config
* bugz/argparsers.py: Default values of non-set arguments are None.
config: Make the configuration work

* bugz/cli.py: Handle (1) defaults, (2) configs, (3) options.
* bugz/configfile.py: Add dump() method to connection, set some defaults.
* bugz/cli.py:  Add missing import
config:  Default query bug status on per-connection basis

* bugz/cli.py: Use query status (a) from options and (b) from
  configuration files.
* bugz/configfile.py: Add 'query_status' attribute into Config class.
* bugz/cli.py: Better log search options.
Configuration files added/edited.

* conf/conf.d/gentoo.conf: Default query statuses.
* conf/conf.d/redhat.conf: Likewise.
* conf/pybugz.conf: Comments.
* bugzrc.example: Remove unnecessary file.
log: Use consistent logging interface

* bugz/argparsers.py: Add new --debug option.
* bugz/cli.py: Switch to log_* interface.
* bugz/configfile.py: Option > config.  Some debug level changes.
* bugz/log.py: New methods setDebugLvl() & setQuiet().
* bugz/cli.py: Remove unnecessary methods.