Rename ambiguous methods with immutable and mutable variants

[jmalloc]

filter / filtered --> filter / copyAndFilter
sort / sorted --> sort / copyAndSort
merge / combine --> merge / copyAndMerge
append / join --> append / copyAndAppend
apply / map --> map / copyAndMap

There is no mutable version of AssociativeInterface::project ?

[jmalloc]

@ezzatron trying to get some more consistent naming going here, thoughts?

[ezzatron]

I'd probably prefer past-tense, but apart from that they look okay.

[jmalloc]

• Collection::filtered() renamed to filter()
• AssociativeInterface::combine() renamed to copyAndMerge()
• IterableInterface::filtered() renamed to copyAndFilter()
• IterableInterface::map() renamed to copyAndMap()
• MutableIterableInterface::apply() renamed to map()
• SequenceInterface::sorted() renamed to copyAndSort()
• SequenceInterface::reversed() renamed to copyAndReverse()
• SequenceInterface::join() renamed to copyAndAppend()
• Set::isStrictSuperset() renamed to isProperSuperset()
• Set::isStrictSub() renamed to isProperSubset()
• Set::complement() renamed to diff()
• Set::complementInPlace() renamed to diffInPlace()
• Added Set::isIntersecting()
• Added Set::symmetricDiff()
• Added Set::symmetricDiffInPlace()

[jmalloc]

I hate 'copyAnd' now :(

[ezzatron]

Copìand will not stand for this injustice.

[jmalloc]

Ok, let's try again.

• append -> appendInPlace
• join -> append
• apply -> mapInPlace
• combine -> merge
• filter -> filterInPlace
• filtered -> filter
• merge -> mergeInPlace
• reverse -> reverseInPlace
• reversed -> reverse
• sort -> sortInPlace
• sorted -> sort

So, the only shit one now is "appendInPlace". HALP.

[jmalloc]

Reverted join/append to original names.