Merging path and url for resources

At the moment we have path and url. I originally had this to make it super easy for tool implementors (no lists of web protocols to match against `http://, https://, ftp://, etc).

At the same time it adds cognitive complexity to the spec and for publishers and confusion about whether one could use both #223 #232

The approach would be probably going forward just to have path and define like:

the location of the resource specified either as a fully qualified url or a unix-style path.
Data Packages may be found online or locally on disk and path should be interpreted
relative to that context (on disk it is a file path, online it is a url path). 

If a relative path is used it is interpreted relative to the base directory for the data
package (the parent directory of the datapackage.json).

Examples:

http://ex.datapackages.org/big-csv/my-big.csv
/examples/my-csv.csv  # absolute path
examples/my-csv.csv   # relative path

[pwalsh]

@rgrp do you have a PR in the wings for this? I think the wording for the spec should be quite straight forward. I think we should also have a set of clear examples alongside that that addresses some of the above points.

Again here, I think in the various places this has been discussed, there is general agreement that it simplifies the prep of a data package for a publisher, and reduces ambiguity in multiple properties that do essentially the same thing, at the relatively small cost of implementing code needing to handle the file pointer disambiguation (fs vs http).

Any comments from the @frictionlessdata/specs-working-group before we start the PR process?

[pwalsh]

So @rgrp I’m in agreement with your points:

• Merge to path and allow it to be a full url (makes semantic sense: “path to the resource file”)
• Deprecate url
• Require implementors to do some regex’ing to distinguish urls from relative paths

Additionally, cache should be implemented, and follow the same rules. (worth mentioning here for the possibility that users were relying on presence of both url and path to keep local copies of remote resources.)

@roll @amercader @akariv @vitorbaptista you are all writing code around this in various places. What do you think?