Close #596

Close #581

Close PyCQA/pylint#2267

Remove the copying of extra_context, since the object is already not mutated. Discovered during #588

This would introduce a new method of configuring astroid & pylint, while the
usual approach we used so far was to set a flag in the MANAGER itself it we'd
need to customize some behaviour (extension_package_whitelist and friends).

Also renamed the flag to `max_inferable_values` to be more suggestive on what it does.

spot performance issues.

Add new envrionment variable call ASTROID_MAX_INFERABLE to tune
the max inferable amount of values at a time.

Close #579
Close PyCQA/pylint#2251

See #581

Ignore non-string keys

Add context_lookup to the context class as extra_context.

Deliver the correct context with the correct boundnode
for function argument nodes.

Close #177

At the moment `load_from_module` is resolving all paths in `sys.path`
to validate that the module being import is in a folder part of the
path. This is done to resolve symlinks.

This can be an issue though it both the file being imported and the path
in `sys.path` resolve to different locations. Even if the symlinks are
importable, the resolution of the paths in `sys.path` might not.

The precedence and associativity rules of operators are respected
and parens are only wrapped around child nodes when needed

A single If node inside the else block is output as `elif`

Unneccesary parens in with statements are removed

Unneccesary parens in tuple returns are removed

Doc strings in classes and functions no longer get additional indenting

There's something going on with io/_io on PyPy. io has all its members coming from _io,
but _io's members themselves are also coming from _io, so astroid cannot find the actual
place where they are defined.

Code in multiple places had the same pattern
for infering call results.

Call the dunder call method if available from a custom metaclass

Note: I had to give ClassDef metaclass lookup a context to prevent a
Recursion

This was overlooked in the initial implementation of
_multi_line_block_fields.

See https://github.com/PyCQA/pylint/pull/2209

Complete refoundation of the numpy_core_numerictypes_transform method thanks
to a deep analysis of the numpy.core.numerictpyes module. The generated hierarchy
of classes is closer to the real one.

Calling object.__new__ on a Const node would result in infinite recursion

Fix infinite recursion by explicitly raising AttributeError if
__getattr__ is called for value

See https://nedbatchelder.com/blog/201010/surprising_getattr_recursion.html
for more details

Close #565