breaking change: normalize fields and flatten output

[hacdias]

This normalizes the object fields names by lower casing them. It also flattens the output of files.ls.

files.ls now returns an array of objects like:

{
	name: 'something',
    type: 0,
    size: 0,
    hash: 'something'
}

files.stat now returns an object like:

{
    type: 'file',
    size: 0,
    hash: 'something',
	blocks: 152,
	cumulativeSize: 0
}

[hacdias]

@diasdavid mind taking a look at this?

[daviddias]

@hacdias a "refactor" that changes the output is not a refactor, it is a breaking change. It is justified? Do we need it?

[hacdias]

@diasdavid it is not strictly necessary, but it has a good justification: consistency. I'm trying to make js-ipfs-api consistent all over (just like what I did on #669).

I can also specify this on interface-ipfs-core because this functions are not there yet.

[hacdias]

Ping @diasdavid

[daviddias]

sounds good @hacdias