tag future tense verbs

[ThijsVroegh]

This pull request introduces the ability to tag future tense verbs in the action analysis module. It includes updates to both the backend logic for tagging verbs and the user interface to support this new feature. This solves issue #93

Backend changes:

• Added support for tagging future tense verbs in the __postag_sents and postag_text methods by introducing a new future_vbz parameter.
• Added the future_verb column to the complete_data_columns list in the Tagger class.
• Implemented the __process_dutch_future_verbs method to identify future tense verbs in Dutch.
• Updated the __parse_tagged_story method to include future tense verbs in the story dataframe.

UI changes:

• Added a checkbox for "Actions - future tense" in the OWSNActionAnalysis widget.
• Updated the show_docs method to pass the future_vbz parameter.
• Added a new HTML mark style for future tense actions.

[eriktks]

tok[5] contains the story_navigator_tag, not the token text. Use in tok[2] instead

[eriktks]

I have tested the code and examined the changes. In the changes tok[5] should be replaced by tok[2] to get the text_value. Otherwise the code changes look fine. The tests were mostly fine. There was one exception: in "zullen en willen vergeten" where "willen" was tagged as future verb. This could have been avoided by checking the dependency relations but this is something which can be done later. Thanks for this work!