l18n: update messages.pot and app.fil

add l18n support to variable table in CodeFileEditor (python/C extension)

set project name and character set in generated messages.pot

close DurationEditorDialog on ENTER key

add button to ForceVariableDialog to toggle forced boolean value

Button is added only for boolean variables.

fix problem with hidden FindInPou dialog with wxPython 3.0 on Windows

FindInPou.IsShown() returned True, but dialog was hidden.
At same time On GNU/Linux with wxPython 3.0 there wasn't such problem.
So it's Windows specific.

enable non-latin variable descriptions in CodeFileEditor

fix following backtrace:

UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-7: ordinal not in range(128)
Traceback (most recent call last):
File "beremiz/editors/CodeFileEditor.py", line 610, in GetValue
return str(self.data[row].get(self.GetColLabelValue(col, False), ""))
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-7: ordinal not in range(128)

disable empty coils and contacts in LD/SFC editors

Closes #30

remove debug code

make all dialog have non-fixed size

this fixes the problem, that some controls may be hidden in some cases, because
dialog size is too small. This can happen when system fonts are bigger
than expected, default system them controls are bigger or if localized
strings are bigger than in English.