Fixed version number update in docs files
Added NXF_WORK variable to define default scratch path
Improved getBaseName() method
Refactored CacheHelper to native Java class
Added support for invariant hash code for Sets and unordered collections
Improved error message reporting
Removed dependency on Picard library
Fixed test
Enhanced splitters the following parameters: 
- limit: limits the maximum amount of retried records 
- decompress: handles gzipped files 
- meta: adds meta-data information as the second parameter to splitting closure
Refactored TupleList to ArrayTuple and UnorderedList to ArrayBag
Do not close splitter channel when an exception is raised
Improved operators parameters validation
Added to collectFile operator ability to sort by using a Comparator object
Added fasta() and fastq() handler factory methods
Added default name when collectFile is used without specifying 
a target file name
Added 'groupTuple' and 'ifEmpty' channel operators
Improved 'groupBy' operator
Added 'empty' channel factory method
Use a Bag collection instead of a list when collecting 
process input files so that insertion order do not invalidate
(eventually) existing cache entries
Code clean-up
Improved docs