Fallback to the term slug if a label does not exist in list-table

Relates to #214
[issue-309] Add `get_changed_keys` method
[issue-309] Doc for new method
[issue-309] Return difference of arrays
[issue-309] Remove numeric indexes
[issue-309] Treat missing keys as differences
[issue-309] Add method to log theme modifications
[isue-309] Use updated option calback
[issue-309] Use improved keys comparison method
[issue-309] Add translations to header mods
[issue-309] Pass context as argument
[issue-309] Add translated labels for background options keys
[issue-309] Add context labels
[issue-309] Use context slug
[issue-305] Display link under Stream settings logs
[issue-305] Filter action link url
[issue-305] Pass record as argument
[issue-305] Set URL to Stream settings
[issue-305] Log option_key meta
[issue-305] Find proper tab