Implement DataFrame.swapaxes

[xinrong-meng]

ref #1929

Implement DataFrame.swapaxes

        >>> kdf = ks.DataFrame(
        ...     [[1, 2, 3], [4, 5, 6], [7, 8, 9]], index=['x', 'y', 'z'], columns=['a', 'b', 'c']
        ... )
        >>> kdf
           a  b  c
        x  1  2  3
        y  4  5  6
        z  7  8  9
        >>> kdf.swapaxes()
           x  y  z
        a  1  4  7
        b  2  5  8
        c  3  6  9
        >>> kdf.swapaxes(i=1, j=0)
           x  y  z
        a  1  4  7
        b  2  5  8
        c  3  6  9
        >>> kdf.swapaxes(i=1, j=1)
           a  b  c
        x  1  2  3
        y  4  5  6
        z  7  8  9

[codecov-io]

Codecov Report

Merging #1946 (29560a6) into master (138c7b8) will decrease coverage by 0.93%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1946      +/-   ##
==========================================
- Coverage   94.64%   93.71%   -0.94%     
==========================================
  Files          49       49              
  Lines       10818    10717     -101     
==========================================
- Hits        10239    10043     -196     
- Misses        579      674      +95     

Impacted Files	Coverage Δ
databricks/koalas/missing/frame.py	100.00% <ø> (ø)
databricks/koalas/frame.py	96.75% <100.00%> (ø)
databricks/koalas/usage_logging/__init__.py	25.66% <0.00%> (-66.65%)	⬇️
databricks/koalas/usage_logging/usage_logger.py	47.82% <0.00%> (-52.18%)	⬇️
databricks/koalas/__init__.py	81.25% <0.00%> (-9.38%)	⬇️
databricks/conftest.py	96.61% <0.00%> (-3.39%)	⬇️
databricks/koalas/testing/utils.py	79.12% <0.00%> (-1.40%)	⬇️
...ricks/koalas/tests/plot/test_series_plot_plotly.py	95.83% <0.00%> (-0.47%)	⬇️
databricks/koalas/generic.py	92.79% <0.00%> (-0.13%)	⬇️
databricks/koalas/plot/matplotlib.py	93.23% <0.00%> (-0.12%)	⬇️
... and 17 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 138c7b8...1dffe07. Read the comment docs.

[ueshin]

Otherwise, LGTM.