Finalized lilypondfiletools package contents.

Removed lilypondfiletools.make_time_signature_context_block() function.

The function is now a private helper to
lilypondfiletools.make_floating_time_signature_lilypond_file().

The lilypondfiletools package now implements the following:

    * lilypondfiletools.Block
    * lilypondfiletools.ContextBlock
    * lilypondfiletools.DateTimeToken
    * lilypondfiletools.LilyPondDimension
    * lilypondfiletools.LilyPondFile
    * lilypondfiletools.LilyPondLanguageToken
    * lilypondfiletools.LilyPondVersionToken

    * lilypondfiletools.make_basic_lilypond_file()
    * lilypondfiletools.make_floating_time_signature_lilypond_file()

MILESTONE: lilypondfiletools refactoring is complete for the 2.15 release.
Merged master.