Added support for crux output

[nbollis]

Added support for reading and writing a .txt output from crux and Shortreed's request.

[codecov]

Codecov Report

Attention: Patch coverage is 93.22034% with 4 lines in your changes missing coverage. Please review.

Project coverage is 75.30%. Comparing base (cfc2f28) to head (03f1342).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #774      +/-   ##
==========================================
+ Coverage   75.27%   75.30%   +0.03%     
==========================================
  Files         195      197       +2     
  Lines       30482    30541      +59     
  Branches     3059     3064       +5     
==========================================
+ Hits        22944    22999      +55     
- Misses       7024     7026       +2     
- Partials      514      516       +2     

Files	Coverage Δ
mzLib/MzLibUtil/ClassExtensions.cs	100.00% <100.00%> (ø)
...ernalResults/IndividualResultRecords/CruxResult.cs	100.00% <100.00%> (ø)
...ders/ExternalResults/ResultFiles/CruxResultFile.cs	90.47% <90.47%> (ø)
mzLib/Readers/Util/SupportedFileTypes.cs	97.05% <50.00%> (-2.95%)	⬇️