Re-include plugins in setup.py packages

[Nodd]

Fixes #3210 (comment)

I forgot this change when switching to flask model.

[goanpeca]

Joselito, could you go to gitter?

[Nodd]

I'm trying, but the network is really bad here so I'm not sure if it will work at all 😞

[ccordoba12]

@Nodd, you also need to change this line:

https://github.com/spyder-ide/spyder/blob/master/MANIFEST.in#L2

Note: The Appveyor failure is unrelated to this change ;-)

[ccordoba12]

There are also a couple of other references to spyplugins. Please remove them too.

[Nodd]

I removed some preferences, and used plugins instead of spyplugins for the user directory (the wiki will have to be updated).

What's left:

• continuous_integration/appveyor/modules_test.bat:124 : I don't know what it's doing exactly. I'm not sure that it's needed.
• .pot and .po files : I'm not sure if I can simply use sed to update these or will it mess things up ?

[ccordoba12]

continuous_integration/appveyor/modules_test.bat

I'll fix this, don't worry about it.

I'm not sure if I can simply use sed to update these or will it mess things up ?

Yeah, please use sed to update them.

[Nodd]

I updated the files but the translations are not loaded. 😞

[Nodd]

Everything seems to work now, except the appveyor thing.

The testing error is unrelated to my changes::

Error: HTTPError: 500 Server Error: Internal Server Error for url:
    https://repo.continuum.io/pkgs/free/linux-64/sqlite-3.13.0-0.tar.bz2
    https://repo.continuum.io/pkgs/free/linux-64/sqlite-3.13.0-0.tar.bz2

[ccordoba12]

Failures seem related to internal problems with conda.

[Nodd]

No failures anymore !