support DataFrames in features

[jgrewe]

unifinished!

[lgtm-com]

This pull request introduces 2 alerts when merging 96ebeb4 into 1875eec - view on LGTM.com

new alerts:

• 2 for FIXME comment

[lgtm-com]

This pull request introduces 2 alerts when merging c2b10bb into ec18e56 - view on LGTM.com

new alerts:

• 2 for FIXME comment

[codecov]

Codecov Report

Merging #829 (c0f4300) into master (e6802d4) will decrease coverage by 0.10%.
The diff coverage is 90.00%.

❗ Current head c0f4300 differs from pull request most recent head ef78e15. Consider uploading reports for the commit ef78e15 to get more accurate results

@@            Coverage Diff             @@
##           master     #829      +/-   ##
==========================================
- Coverage   95.70%   95.59%   -0.11%     
==========================================
  Files         201      201              
  Lines       13657    13838     +181     
==========================================
+ Hits        13070    13229     +159     
- Misses        587      609      +22     

Impacted Files	Coverage Δ
include/nix/MultiTag.hpp	100.00% <ø> (ø)
include/nix/Tag.hpp	100.00% <ø> (ø)
include/nix/base/IBaseTag.hpp	100.00% <ø> (ø)
include/nix/base/IFeature.hpp	100.00% <ø> (ø)
test/BaseTestFeature.hpp	100.00% <ø> (ø)
src/MultiTag.cpp	79.59% <50.00%> (-4.13%)	⬇️
src/Feature.cpp	78.12% <64.70%> (-16.32%)	⬇️
src/util/dataAccess.cpp	89.27% <66.66%> (-0.31%)	⬇️
include/nix/Exception.hpp	91.52% <75.00%> (+0.45%)	⬆️
src/Tag.cpp	89.15% <88.88%> (-0.18%)	⬇️
... and 9 more

---

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[lgtm-com]

This pull request introduces 2 alerts and fixes 1 when merging 663b237 into c865fd0 - view on LGTM.com

new alerts:

• 2 for FIXME comment

fixed alerts:

• 1 for Virtual call from constructor or destructor

[lgtm-com]

This pull request introduces 2 alerts and fixes 1 when merging ef78e15 into e6802d4 - view on LGTM.com

new alerts:

• 2 for FIXME comment

fixed alerts:

• 1 for Virtual call from constructor or destructor