Dewi-commands

- MainApplication: --debug implies --log-level debug
default log level: info
- images/filedb: add count() to count entries in photo_file_info table
- images related dewi_commands.commands: use exiftool-5.26 as MacPorts updated it
- safe_delete_images: handle Exceptions at unlink(), mainly PermissionErrors
- add further log_*() calls into dewi.rrdtool & realtime_sync

- pretty-print output command list (e.g. 'list-all')
- add dewi.utils.archive, which contains an UnZip class to (partially) unzip
.zip files
- if a command is mistyped or non-existing, print at most 6 similar command
names, or list all of them
- dewi_commands.common.images.filedb: add rollback() method to FileDatabase
- dewi_core.context: Context got 'dewi_commands.commands' and 'command_registry'
properties, and always contains the corresponding 'dewi_commands.commands' and
'commandregistry' fields
- introduce dewi_core.logger module, log_debug, log_info, etc. can be used

- fix setup.py

- add Connection class and ensure_connection() method to kayako module
to reuse calculated signature and provide an object for easier testing
- config/node: add NodeList and also test the module
- rrdtool: use NodeList & fix modifiers
- NetworkCardVendors: add option to prevent network usage
- logparsers: add support to add multiple callbacks to a pattern:
during log processing one pattern matching - multiple calls.
And ensure that '\n' (0x10) is handled only as log line separator
- add lithurical command to print events of a calendar year
- kayako: add TicketStatus and TicketStatuses classes

- add support of generating .PNG files from .rrd files in a munin directory
- dewi.utils.yaml: add the module to save a dict to a YAML file
- config/node.py: add Node.load_from() to load from a dict (from eg. YAML);
- config/node: __setattr__ checks whether key is already in the node
- config/config: add _top_level_unsafe_set() used by subclasses, for self[key] = value
- logparser: add ISO8601Parser.to_datetime, reuse it in to_timestamp
- dewi_core.application: add list and list-all dewi_commands.commands, w/o args 'list' is used

- It can be marked as stable.
- Changed to LGPL, to use freely in proprietary code (eg. by me)