Pushing collection{,WithDuplicates} down from base class
Fixed base testFirstN, using it in ArrayTest
SequenceableCollection subtree tests now use literals mostly

Plus fixed some errors in tests, which were hidden by inheritance.
'fixture' protocol, commented some base class methods
sampleXxx fixture methods, Indexable base tests use it

Plus removed specialized tests since inherited is better.
Error in Array and String are uncovered.
ifPresent:{,ifAbsent:} tests at base, removed subtests

Eigth errors stemming from two bugs.
Fixing errors with {String,Array} >> at:{,IfPresent:}ifAbsent:
testDo runs with collectionWithDuplicates as well
base testAtPut for all IndexableCollections
test collection size in base
Fixing TestRunner failure, returning ^nil to collectionClass
testAddAll, testComma
{coll,sel,det}ect tests, nonValue merged w/ newValue
detect:ifNone: test
SetTest is now in CollectionTest hierarchy

Bug in Set uncovered: removeAll not implemented
Fix missing removeAll in Set
Clarifications
Use self collectionSize for SequenceableCollection borders
Merge pull request #783 from herby/do-not-test-implementation

Do not test implementation