Fix CP2k 2026.1 input files

[hejamu]

The 2026.1 release of CP2k introduces an interface to SMEAGOL. Since SMEAGOL uses dots (.) to mark subsections in its parameters and CP2k mirrors all the inputs, pycp2k does currently not work with the new CP2k version.

The error only arises at runtime:

>>> import pycp2k
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    import pycp2k
  File "./repos/pycp2k/pycp2k/__init__.py", line 1, in <module>
    from .cp2k import CP2K
  File "./repos/pycp2k/pycp2k/cp2k.py", line 3, in <module>
    from pycp2k.classes._CP2K_INPUT1 import _CP2K_INPUT1
  File "./repos/pycp2k/pycp2k/classes/_CP2K_INPUT1.py", line 7, in <module>
    from ._force_eval3 import _force_eval3
  File "./repos/pycp2k/pycp2k/classes/_force_eval3.py", line 6, in <module>
    from ._dft1 import _dft1
  File "./repos/pycp2k/pycp2k/classes/_dft1.py", line 34, in <module>
    from ._smeagol1 import _smeagol1
  File "./repos/pycp2k/pycp2k/classes/_smeagol1.py", line 2
    from ._bs.subsystemsboundaries1 import _bs.subsystemsboundaries1
                                              ^
SyntaxError: invalid syntax

This PR adresses this the same way PLUS signs are handled, replacing occuronces of . by DOT.