Conjugation and declension (#590)

* fix duplicated download screen in nav stack

* fix: reset to Installation tab's root when app is reopened

* init add contracts and update query nouns

* "Noun annotation: update queryNounForm based on gender contract"

* Restore DACommandVariables.swift

* Plural command: update query for plural command and add plural annotation

* Noun annotation: fix multiple annotation case

* Preposition annotation: update queryPrepForm and add conversion preposition to abbreviation

* Conjugate: use dynamic conjugation and declension

* Declension: move declension contract to main contract file

* Conjugation and declension: add function documentation and fix comments

* Add YAML version of data contracts

* Minor fix in comment in contracts

* feat: change to using YAML contract

* Add in missing displayValue fields for German declension

* fix: starting index for declension

* Update contracts with fully indexed conjugations and declensions

* Add .gitkeep to maintain directory when contracts are removed

* fix: contract typo

* fix order conjugation and declension

* Misc formatting and comment fixes

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Co-authored-by: Andrew Tavis McAllister <andrew.t.mcallister@gmail.com>

Author: catreedle