Import from Anki for full sync

After importing a file the user should be able to review each AnkiCard item before applying it to or creating VocabItems. For that decide the List of AnkiCards into the following collapsible categories:

[x] 1. Cards which where matched by AnkiGuid and require no update of the VocabItem (except timestamps)
[x] 2. Cards which where exactly matched by Hanzi (only 1 match) and require no update of the VocabItem except AnkiGuid (and timestamps)
[x] 3. Cards which had no match, neither by AnkiGuid nor by Hanzi.
[x] 4. Cards which where matched by AnkiGuid and but require a update of the VocabItem
[x] 5. Cards which where exactly matched by Hanzi (only 1 match) but require an update
[x] 6. Cards which had multiple matches

Then:

[x] For each category with 0-1 matches, offer one central button to create/update all the VocabItems.
[x] For each item offer the option to review it individually and apply it to a VocabItem

Additionally:

[x] ~~store export file timestamp (or is timestamp of applying changes better!? Think about the pros and cons)~~ -> storing timestamp of applied changes is better to determine the need for export later (i.e. changes since last import). The problem of ever-changing timestamps isn't relevant anymore once the latest import file and remaining AnkiCards are persisted.
[x] persist the latest imported file, to avoid repetitive importing and for later comparison when exporting
[x] persist which Anki cards have been applied and which ones are still waiting, to avoid repetitive importing/applying

related to:

Waog / heisig-translator-website

Import from Anki for full sync #55

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