Parsing improvements and more misc stuff

[Vindaar]

Some fixes to spread and adds few helpers (see changelog). Mainly fixes issue #58 about parsing of CSV files with quoted fields (I hope fully).

Full changelog:

* v0.4.0
- add ~shuffle~ to shuffle a DF. Either using stdlib global RNG or
  given RNG
- add ~extend~ helpers for ~seq/Tensor/Column~ to add a single element
  to any collection and return the extended version
- throw custom ~OSError~ if CSV file cannot be read
- add =%~= for ~(string, T)~ to construct a ~VObject~ Value
- fix ~spread~ implementation if more keys are present
- correctly handle quoted fields in CSV files, fixes issue #58
- add ~allowLineBreaks~ option to also allow for line breaks in quoted
  fields. It's an optional option (despite being commonly useful for
  files with quotes), because counting the lines is otherwise a useful
  sanity check the parsing worked successfully.  
- [IO] fix for space separated files with quoted fields as columns