BitSet.h: explicitly include SetCoverInstance.h
BitSet: implement getAll{Sets,Elements}From
BitSet: make covering{Sets,Elements} private
SetCoverBenchmarker: fix an error message
SetCoverBenchmarker: check if cover returned by algorithm is complete
BitSet: fix a mistake in a comment
SetCoverInstance: change the order of function definitions / declarations

There was a mess.
LoopAllCollections: some modifications

The class is not yet ready for use
SetCoverInstance: fix reading the stuff from the stream
Update TODO
SetCoverBenchmarker: add support for passing size of best solution

Sometimes when we are running without an exact algorithm,
it is sensible to check whether a solution does not appear too small,
which would be usually a result of a bug in the exact algorithm.
SetCoverBenchmarker: fix a bug
LoopAllCollections: do not use the Duff's device
LoopAllCollections: declare all defined functions, make some functions private
LoopAllCollections: finish writing content

Small note: recreateStack now does not have to handle cases when the
stack is empty, it is guaranteed that it will not be called with an
empty stack.
LoopAllCollections: small correctons that fix compiler errors
LoopAllCollections: shorten too long lines

Also involves making many names shorter.
LoopAllCollections: limit all lines to 80 characters.
LoopAllCollections: rename minimalCollectionSize -> minCollectionSize

This also fixes a serious bug: the value of that variable was not
initialized.
BitSet: use libstdc++ extensions when available to get some speedup

//Modified with git rebase to correct a compilation error