Utilize JSONAdapter to simplify ComposerAdapter
list type for sheet music querying.
Basic skeleton code finished.
Needs UI suger-coating.
added spinning progressbar to composerView
Merge branch 'sheetListView'
renaming files
renamed activity_sheet -> fragment_sheet
renamed activity_composerview_item -> adapter_composerview_item
Added intent to invoke a SheetView from a SheetListView
ComposerView now invokes SheetListView to get a list of the corresponding composer's works.