Custom where condition for NetteDatabaseDataSource

[vcernik]

Adds custom where condition for NetteDatabaseDataSource

[radimvaculik]

LGTM. But seems like breaking change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.97%. Comparing base (e5faff0) to head (ed8914d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1283      +/-   ##
==========================================
+ Coverage   46.79%   46.97%   +0.18%     
==========================================
  Files          53       53              
  Lines        2729     2729              
==========================================
+ Hits         1277     1282       +5     
+ Misses       1452     1447       -5     

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[vcernik]

Yes, it seems. But when previous getDataSource returns Explorer, it's completely useless - there is no logical connection to object NetteDatabaseDataSource.

I hope I'm making myself clear. I'm excited - this is my first PR :D Thank you for this awesome Datagrid! Hezký den ;)