Don't blow on bundle update gem when lock is not present.

* rename not_found_message to gem_not_found_message
* add lock_not_found_message
* add GemfileLockNotFound error with 22 status code
remove exit code conflict with VersionConflict
fix NoMethodError when binstubs errors

/cc @Who282
whitespace style
Merge pull request #2840 from zizkovrb/bundle-update-message

Don't blow on bundle update gem when lock is not present.

Conflicts:
	lib/bundler/cli.rb