Feature/corpus settings

[lukavdplas]

Finally got around to implementing this. Changes the corpus settings format according to #2099

The new format can exist side by side with the old one (you could even use both formats in the same corpus) but it should fully replace it.

For some corpora, I've changed the definition so they support the new format as well as the old one (but there is a log warning if you use the old setting). This adds a significant expansion of code, which is temporary. For example, this was the ParliamentCanada definition:

class ParliamentCanada(Parliament, CSVCorpusDefinition):
    title = 'People & Parliament (Canada)'
    description = "Speeches from House of Commons"
    min_date = datetime(year=1901, month=1, day=1)
    data_directory = settings.PP_CANADA_DATA
    es_index = getattr(settings, 'PP_CANADA_INDEX', 'parliament-canada')
    word_model_path = getattr(settings, 'PP_CANADA_WM', None)

Now changed to:

class ParliamentCanada(Parliament, CSVCorpusDefinition):
    title = 'People & Parliament (Canada)'
    description = "Speeches from House of Commons"
    min_date = datetime(year=1901, month=1, day=1)

    @property
    def data_directory(self):
        return get_deprecated_setting('PP_CANADA_DATA') or super().data_directory

    @property
    def es_index(self):
        return get_deprecated_setting('PP_CANADA_INDEX') or 'parliament-canada'

    @property
    def word_model_path(self):
        return get_deprecated_setting('PP_CANADA_WM') or super().word_model_path

After deployment, this can be changed to:

class ParliamentCanada(Parliament, CSVCorpusDefinition):
    title = 'People & Parliament (Canada)'
    description = "Speeches from House of Commons"
    min_date = datetime(year=1901, month=1, day=1)
    es_index = 'parliament-canada'

Changes to Django settings

This adds the CORPUS_SETTINGS Django setting. No immediate change is required, but the log will show a warning if a corpus can be switched to CORPUS_SETTINGS and this has not been done in the environment.