Update mail log if exception is thrown

[sypets]

Resolves: #57

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1. Catch exception on send() and update tx_maillogger_domain_model_maillog
2. In case of exception write $->getMessage() to tx_maillogger_domain_model_maillog
3. Mark logs with error in "Mail Logger" list view by using an icon
4. Instead of showing "Accepted recipients: 1", name the field "Result" and show error message, if error message exists
5. add extra field "status" with numeric value

This might still benefit from fine tuning:

• make it pretty
• localize some more texts

Example output:

list:

detail:

[Kanti]

@sypets Thank you so much for the awesome enhancement! I've made a few small adjustments and just released it in version 4.1.0.

[sypets]

@Kanti Thank you so much. I have been on holiday, will take a look next week.