[cleanup] Remove spurious marker from old version control system
Canonicalize single-inclusion guards
[documentation] Use \tparam to document template parameters
Make the index type a configurable template parameter

Previously the type was hardwired to 'int'.  Int is still the default
value for the new parameter, for backward-compatibility.
Use IndexSet::IndexType as the type for indices, rather than hardwiring 'int'
Use the index type exported from the mapper, rather than expecting 'int'
[cleanup] Remove some boiler-plate code