prompt: pass argv parameter to run_prompt_command
prompt: allow search patterns with spaces in them

For example: bind stage D :/^diff --git
Introduce a macro for all enum macros
Add file-filter option
Introduce :toggle prompt command

This moves most toggle actions to use the new :toggle prompt command.
Use :toggle binding for diff context manipulation

Retire the diff-context-up and diff-context-down actions in favour
of the new `:toggle` infrastructure.