PR: Make value_to_display more robust

[ccordoba12]

Fixes #4221

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This PR

1. Improves how any object is displayed in the Variable Explorer. Now objects will be shown as foo object of bar module (except for know objects, like Dataframes).
2. Doesn't try to display subclasses of list, dict and tuple, to avoid things like issue Spyder stops executing commands if Variable explorer shows complicated objects #4221 (which was using a generalization of a dict that doesn't have an optimized repr).
3. Applies value_to_display recursively to the elements of lists, dicts and tuples. This prevents freezes in the Variable Explorer when people add objects with huge repr's as elements of those collection types.

Screenshots:

Before

After

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TODO:

• Tests

[skip pep8]

[pep8speaks]

Hello @ccordoba12! Thanks for updating the PR.

• In the file spyder/widgets/variableexplorer/utils.py, following are the PEP8 issues :

Line 259:5: E722 do not use bare except'
Line 335:80: E501 line too long (81 > 79 characters)
Line 365:21: E722 do not use bare except'

Comment last updated on August 26, 2017 at 22:15 Hours UTC

[goanpeca]

@ccordoba12 could you add a scrrenshot of how it looks?

[ccordoba12]

@goanpeca, I updated the description of this PR and added before/after screenshots.

@jitseniesen, what do you think about this one?