Added
- `Uci.add` function for adding anonymous section implemented
- `EUci.add` function to add both anonymous and named sections added

Added
* `convert` argument for `EUci.get`. It provides a way to convert values
  to any type with custom function.

Changed
* `list` argument for `EUci.get` is now required to be set to `True` for
  lists otherwise only first value is returned. This is removal of
  auto-detection of lists. The get of list has to be now always
  explictly stated.
* `dtype` argument for `EUci.get` can now be any type that can be
  initialized with string as a single argument (such as `int("42")`.
* `default` argument for `EUci.get` now uses object instance `NoDefault`
  to detect that there is no default instead of presence of keyword
  argument.

Removed
* obsolete "get" methods in `EUci`

This also completely removes Python2.

This is in some corner cases incompatible change.

The incompatible changes here are:
* The raised exception in case of conversion error is no longer
  ValueError but rather UciExceptionNotFound.
* The list argument now always has to be specified to `list=True` for
  list of configs. There is no longer a mode when either tuple or value
  is returned. It is one or the other depending on list argument.
* No default is now detected using dedicated NoDefault object instance
  instead of using presence of the argument. In most cases this affects
  nothing.

The new convert argument adds an easy way to convert values to any type
by providing lambda function that implements such conversion.

This way we can support any type that can be initialized from string and
exception depends on type called tries to convert string into.

Support was added in 02db2708.

Fixed
* missing include `collections.abc` in `euci` module

We have to import collections.abc instead of plain collectons as it does
not contain abc.
This fixes issue introduced by: ebe462fc

Added
* EUci support for IP address parsing

Fixed
* Use of deprecated and in Python 3.9 removed library

Štěpán Henek authored 4 years ago and Karel Koci committed 4 years ago

```
tests/euci_test.py::test_get_string
  /home/stepan/project/pyuci/euci/__init__.py:34: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and in 3.9 it will stop working
    return isinstance(data, collections.Iterable) and not isinstance(data, str)
```

Note that user can use dtype=IPv6Address or dtype=IPv4Address
the result will be IPv4Address or IPv6Address regardless of dtype
settings.

This allows them to be accessible by user if he does not want or can't
use automatic conversion in euci.

When non-tuple default was passed it just converted it to string instead
of iterating over its content.

We were checking if argument is list or tuple but that is technically
wrong. Much better is to just check if it is iterable. Problem is that
string is also iterable but that we can just do as an exception.

Idea of this is that user can set to configuration file instead of list
option but we want to make sure that even if he does that that we get
tuple of values. This is exactly for that case. Setting list to True
ensures that get never returns anything else then list. Where on the
other hand setting list to False causes it to never return tuple even if
value is lists (in which case first found list is returned).

This fixes handling of lists in euci.

This is much more versatile and compact syntax. You can optionally set
default keywords argument and that gives you behavior where
UciExceptionNotFound is never thrown out.
This also adds tests for defaults.

This drops previous get_t and set_t methods in favor of overloaded get
and set methods.
You can optionally add keyword argument dtype to get method to ensure
that returned data is of specified type. For now only str, int and bool
are supported.
set methods now detects value argument type and behaves according to it.
In general it just converts value to string but in case of bool it
replaces it with defined value.