Remove PlaceholderAPI processing from commands

[jpenilla]

Running commands through PlaceholderAPI can cause some edge case issues, see #112.

A solution to this could be removing PAPI processing for command strings and adding our own <player_name> and etc replacements for commands. This would allow the command being executed to handle PAPI if it wants to, or not. This wouldn't impact executing AP commands as they will process the placeholders as part of command execution.

This needs consideration to ensure we don't lose any functionality with this change. Also config upgrading logic will be necessary.