Improve multiline support

[at-ng]

The way multi line works for snippets currently it seems initial white space is ignored. This can be a problem because sometimes you want to start a line with some indentation. One way to solve this would be to change this line from

data[path][snippet_key] = snippet_string

to just something like

data[path][snippet_key] = snippet_string.replace('|||', '')

Then you could start each line where you want to maintain indentation with " |||". Another option would be to do this

data[path][snippet_key] = snippet_string.replace('\\n', '\n')

Then you can maintain the indentation by doing everything on the same line, a bit more annoying to work with though but sometimes it might be better so maybe both could be supported.