Implement symmetric_difference of Index & MultiIndex

[itholic]

https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Index.symmetric_difference.html#pandas.Index.symmetric_difference

>>> s1 = ks.Series([1, 2, 3, 4], index=[1, 2, 3, 4])
>>> s2 = ks.Series([1, 2, 3, 4], index=[2, 3, 4, 5])

>>> s1.index.symmetric_difference(s2.index)
Int64Index([5, 1], dtype='int64')

>>> s1.index.symmetric_difference(s2.index, result_name='koalas')
Int64Index([5, 1], dtype='int64', name='koalas')

>>> s1.index.symmetric_difference(s2.index, sort=True)
Int64Index([1, 5], dtype='int64')

>>> s1.index ^ s2.index
Int64Index([5, 1], dtype='int64')

For MultiIndex

>>> midx1 = pd.MultiIndex([['lama', 'cow', 'falcon'],
...                        ['speed', 'weight', 'length']],
...                       [[0, 0, 0, 1, 1, 1, 2, 2, 2],
...                        [0, 0, 0, 0, 1, 2, 0, 1, 2]])
>>> midx2 = pd.MultiIndex([['koalas', 'cow', 'falcon'],
...                        ['speed', 'weight', 'length']],
...                       [[0, 0, 0, 1, 1, 1, 2, 2, 2],
...                        [0, 0, 0, 0, 1, 2, 0, 1, 2]])
>>> s1 = ks.Series([45, 200, 1.2, 30, 250, 1.5, 320, 1, 0.3],
...                index=midx1)
>>> s2 = ks.Series([45, 200, 1.2, 30, 250, 1.5, 320, 1, 0.3],
...              index=midx2)

>>> s1.index.symmetric_difference(s2.index)
MultiIndex([('koalas', 'speed'),
            (  'lama', 'speed')],
           )

>>> s1.index.symmetric_difference(s2.index, result_name=['a', 'b'])
MultiIndex([('koalas', 'speed'),
            (  'lama', 'speed')],
           names=['a', 'b'])

>>> s1.index.symmetric_difference(s2.index, sort=True)
MultiIndex([('koalas', 'speed'),
            (  'lama', 'speed')],
           )

>>> s1.index ^ s2.index
MultiIndex([('koalas', 'speed'),
            (  'lama', 'speed')],
           )

[codecov-io]

Codecov Report

Merging #953 into master will decrease coverage by 0.08%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##           master     #953      +/-   ##
==========================================
- Coverage   94.52%   94.43%   -0.09%     
==========================================
  Files          34       34              
  Lines        6466     6510      +44     
==========================================
+ Hits         6112     6148      +36     
- Misses        354      362       +8

Impacted Files	Coverage Δ
databricks/koalas/missing/indexes.py	100% <ø> (ø)	⬆️
databricks/koalas/indexes.py	92.11% <95.45%> (-4.34%)	⬇️
databricks/koalas/missing/frame.py	100% <0%> (ø)	⬆️
databricks/koalas/plot.py	94.28% <0%> (ø)	⬆️
databricks/koalas/missing/series.py	100% <0%> (ø)	⬆️
databricks/koalas/frame.py	96.03% <0%> (ø)	⬆️
databricks/koalas/base.py	94.9% <0%> (+0.06%)	⬆️
databricks/koalas/series.py	96.32% <0%> (+0.22%)	⬆️
... and 1 more

---

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[HyukjinKwon]

Why did we skip this @itholic ?

[itholic]

@HyukjinKwon because the way of print out for MultiIndex are different depends on their python version 😲

[HyukjinKwon]

Seems fine.

[ueshin]

Shall we explicitly block the cases MultiIndex ^ Index or Index ^ MultiIndex for now?

[HyukjinKwon]

The tests are being failed after this commit anyway. I will revert this commit. @itholic do you mind opening a PR again to address test failures and Takuya's comment above?

[itholic]

@HyukjinKwon sure, i'm going to address in separated PR.