☂ CSV rework

[Jolanrensen]

I've collected several issues regarding CSV reading / readDelim to be reworked. Most are marked with the new CSV label.
I marked them all, because most are related and solving one will require solving others and vice versa.

Let this issue be an umbrella issue linking to the relevant issues:

• Improve and document CSV reading options  #787
  • Split readDelim and readCsv into different files, possibly a different module?
  • Deprecate .read() overload, this should only exist in guess.kt Deprecating DataFrame.read("", delimiter =) #902
  • KDocs for each overload
  • Check which CSVFormat options we can put in the readDelim and readCsv functions to create overloads without it. (Like setting the quote mark)
  • Keep one overload for readDelim and readCsv with CSVFormat as option so people can set advanced settings with it.
• Allow readCSV to read a folder of CSVs #826
• Bug: DataFrame.readCSV("") returns files in the folder #508
• readDelimiter variant for Regex as delimiter #746
• Cannot handle aligned multi-space-delimited files deephaven/deephaven-csv#212
• Reading CSV with byte order mark bleeds into first Column Name #687
• Incorrect parsing of CSV file. Locale is ignored for some columns #607 Covered by Fast double parser #935
• NPE in FrameColumnImpl.schema property #593 Covered by Fixes nulls in framecols and improves column creation situation #925
• Alternative CSV reader #589
• Read function with just skipLines =  #507
• readCSV fails for *.zip #469
• Library doesn't follow official naming conventions #383
• Split codebase into several subprojects #100
• Reading empty CSV bug #834
• Reading CSV with custom nullString impossible #921
• Replace io.File on nio.Path in DataFrame.read methods #527
• Remove opt-in
• Add a User Guide "How to handle large CSV?" #765
• Extend CsvOption in ImportDataSchema annotation and Gradle Task
• Change drag-and-drop behavior in notebooks
• Documentation about new CSV implementation on the website/examples when it's no longer experimental.
• Move Compression to :core and apply to other io's

[Jolanrensen]

Not all tasks are finished. The "dataframe-csv" implementation is entering experimental stage at the 0.15.X version of DF.
The next version will stabilize it and deprecate the old implementation.