Add merge instruction to update_canavs script.
Only close open contexts.
Avoid opening context with no data.
Replace list with a tuple.

Context value gets passed to a set, which complains, that list is
unhashable.
Display conditions that were loaded from context.
Catch exceptions in sip_getapi.
Tests for encode domain.
Save setting name in setting.
Encode domain always returns two elements.
Tests for settings_from_widget.
Refactor settings_to_widget.
Fixed method signature.
Refactored match.
Refactored select attributes context handler.
Do not try to transfer settings from None context.
Values that are not tuples with two elements are not variables.
Check for None context.
Initialize attributes in __init__.

Nedded, so the widget does not display error, when opened with no data.
Added link to detailed installation guides.
Append git revision to prerelease versions.