Clean up indentation and whitespace

- Stripped trailing spaces
- Replaced mixed indentation styles with one
Make command usage, formatting consistent

- Use consistent command abbreviations
- Use ! with normal where appropriate
- Use nore- mappings where appropriate
- Other misc. formatting
Fix mapping and function scope

- Only set buffer-local mappings
- Use <LocalLeader> rather than hardcoding "\"
- Use script-local functions with <Plug> maps
- Only set default maps if none already exist
Rename plugin file

Users likely already have an ftplugin/php.vim file
Add space after prompt text
Improve placement of extracted class property

- Ensure property is placed in containing class, not next class
- Do not assume opening bracket is on next line