LALPulsar: rename FlatLatticeTiling.[ch] to LatticeTiling.[ch]

- plus rename structures, functions, and constants
- plus more minor edits, whitespace/comment cleanups
LatticeTiling: add XLALGetLatticeTiledDimensions() for returning tiled dimensions

- rename XLALGetLatticeDimensions() to XLALGetLatticeTotalDimensions()
LatticeTiling: replace 'eye_increment' with 'inv_increment'

- is inverse of 'increment' but with non-tiled dimensions set to zero,
  so that they are not disturbed
LatticeTiling: do not store metric in tiling structure

- unneeded after XLALSetLatticeTypeAndMetric()
- separate metric correctness checks from other code