API refactoring; new error handling flow

[psolom]

Changes in the API for v2.7.0

1. getfile API method should be RENAMED to getinfo and return either file or folder stats. Restriction to handle files only should be removed.

2. getfolder API method should be RENAMED to readfolder. No changes in functionality.

3. API methods readfile, getimage and download should USE THE SAME FLOW to read file and write it to the output. The difference will be in headers and restrictions (validation checks) only. Read/Write flow features which should be implemented (preferably):

   • read in small chunks in order to handle big size files;
   • handle HTTP RANGE for media files;

4. editfile API method should be REMOVED, instead of it the readfile is used at the client-side.

5. download API method should be simplified and handled with a single request. Implemented within the commit af60b30

6. The error handling. When fire an error you have to add the following HTTP headers to the response:

        header('Content-Type: application/json');
        header('HTTP/1.1 500 Internal Server Error');

Also API error format sould correspond to JSON API standard. Imlemented within #210

[psolom]

@fabriceci, @gmkll, @jsooter, @stevelittlefish, @jlaustill, @forestlake, @sinanbozkus, @richeflits

I have reworked the API (located at the dev branch). Not great but very important changes to keep consistency and remove confusing things. Please, take a look the list and update the connectors that you are maintained.

@fabriceci, @gmkll, @jlaustill, @forestlake, @sinanbozkus, @richeflits I have made some modifications trying to adjust connectors, but my exprience with non-PHP connectors is not enough to cover all the changes. I don't even have a chance to test the modifications I made, so look through your connectors thoroughly, test updated code and implement the missing features, please. (create PR to the dev branch)

@jsooter, @stevelittlefish Both Python Flask connectors are standalone packages, so I had no chance to modify them. Them will become outdated after the v2.7.0 release. Take care to update your connectors, please.

[psolom]

7. New seekfolder API method, see Search inside all the userfiles #271

[psolom]

8. Modified attributes list in the API response.

Removed "timestamp" attribute. "created" and "modified" attributes now contain unix timestamps instead of formatted datetime strings. Datetime formatting is performed at the client-side now.

[psolom]

Released in v2.7.0