Rewrite Log service

[renatomassaro]

This will be a rather large PR meant to enhance (but mostly rewrite) the Log service.

The biggest improvement is that now logs are structured data with pre-defined types, as opposed to the old Log system who was simply a string, void of any context.

So we changed from:

String: "localhost downloaded file Cracker.crc (1.0) from 1.2.3.4"

to

Struct: {type: :download_gateway, file_name: "Cracker.crc (1.0)", ip: "1.2.3.4", network_id: "::"}

To the end user this change is transparent (the struct will be "translated" to the string above anyways). But this allows for:

• easier/better i18n support
• enhanced log editing support / UI
• easier support on log-based features (e.g. Log X should have field Y updated to contain Z)

---

• [x] Support structured Log format
• [x] Rewrite Log internals
• [x] LogPaginateRequest
• [ ] LogFilterRequest
• [x] LogIndex
• [x] LogHenforcer
• [x] LogForgeRequest
  • [x] LogForgeHenforcer
• [x] LogFactor
• [x] LogForgeProcess
  • [x] Create
  • [x] Edit
• [x] LogRecoverRequest
  • [x] LogRecoverHenforcer
• [x] LogRecoverProcess
  • [x] Global
  • [x] Custom
• [x] LogAddedEvent
• [x] LogRecoveredEvent
• [x] LogRevisedEvent
• [x] LogDestroyedEvent

Incidental

• Removed LogFactory
• Completely removed ex_machina dependency :tada:
• Added tgt_log_id on Process.t struct
• Added set_relay/3 macro for Helix.Factor
• Added SIGRETARGET, i.e. support for recursive process type (#324)
• Added custom pre-hook at Process.Executable

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This change is 

[sourcelevel-bot[bot]]

Ebert has finished reviewing this Pull Request and has found:

• 5 possible new issues (including those that may have been commented here).
• 6 fixed issues! 🎉

You can see more details about this review at https://ebertapp.io/github/HackerExperience/Helix/pulls/410.