Multiple improvements

[Hakun1n]

• Replaced SSH connections towards Transmission host but call the Transmission RPC instead. Remote script is not necessary anymore.
• All user-required vars at the top of the code. (PIA credentials were in the middle)
• Removal of remnant/non-existing functions (like "fatal_error" and/or "verify")
• Suppress log record when there is no port change in three consecutive runs to avoid spamming pfSense system. (Resets upon port change)
• Removal of unnecessary "echo" lines. Everything goes to syslog anyway.
• Minor code polish (all user envs in small letters, quotation marks to prevent unexpected globbing)

[Hakun1n]

@fm407 I hope I've covered all usual situations (host/service down, invalid RPC calls, etc...) anyway there might be some missed scenarios. Also the Syslog shouldn't be flooded by the informational messages when the port does not change.

I'll keep it running on my system for some time and confirm the PR if there are no issues.