#48: Fix ScalaDoc cross-module links

[benedeki]

• fixed ScalaDoc cross-links
• decreased log size on tests running on Spark 3

Closes #48

[github-actions[bot]]

JaCoCo code coverage report - scala:2.11 - spark:2.4

File	Coverage [87.02%]	:green_apple:
DataFrameImplicits.scala	98.69%	:green_apple:
StructTypeImplicits.scala	84.19%	:green_apple:
SparkVersionGuard.scala	75.57%	:x:

Total Project Coverage	85.65%	:green_apple:

[github-actions[bot]]

JaCoCo code coverage report - scala:2.12 - spark:3.3

File	Coverage [87.66%]	:green_apple:
DataFrameImplicits.scala	98.68%	:green_apple:
StructTypeImplicits.scala	95.77%	:green_apple:
SparkVersionGuard.scala	60.94%	:x:

Total Project Coverage	88.63%	:green_apple: