[FIX] Louvain clustering fails when Table or ndarray on input.

[PrimozGodec]

Issue

When Louvain clustering got Orange.Table or ndarray on the input it fails when convertin table to graph.

The way to reproduce:

data = Table("iris")
louvain = Louvain(2)
louvain.fit(data)

Description of changes

Fixed to accept Table or ndarray.
Added tests.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #3618 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3618      +/-   ##
==========================================
+ Coverage   84.07%   84.07%   +<.01%     
==========================================
  Files         370      370              
  Lines       67256    67256              
==========================================
+ Hits        56546    56548       +2     
+ Misses      10710    10708       -2

[codecov]

Codecov Report

Merging #3618 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3618      +/-   ##
==========================================
+ Coverage   84.07%   84.08%   +<.01%     
==========================================
  Files         370      370              
  Lines       67256    67256              
==========================================
+ Hits        56546    56549       +3     
+ Misses      10710    10707       -3