Merge branch 'release/0.8.2' into develop
Rename store_messages feature to history
Refactor commands to group common parameters into CommandContext
Create a record of each outgoing txt with reference to originating txt
Make TxtsRelayAdmins pass through originating_txt_id
Make all commands pass in originating_txt_id

(Emphasises need for refactoring, so many changes, all so similar!)
Add view of message history by subscriber

Closes #5
Link to subscriber txt history from subscriber list
Merge branch 'feature/history' into develop
Update README history
Merge branch 'release/0.8.5'