Lazily compute fingerprints in TM3Tuv

    TM3Tuv.setContent() used to immediately calculate the fingerprint
    on the underlying data object, even if it was never used.  This is
    now done lazily.
remove unneeded executable modes
fix javadoc warnings
clarify lookup docs, param names

- Renamed sourceLocale -> keyLocale, to emphasize that it's the source of
  the matchKey param, not the matched TU.  (This was already done in
  FuzzyIndex methods.)
- Rename targetLocales -> matchLocales, to emphasize that they don't
  necessarily need to be target locales of the match.
- Make the javadoc more explicit, especially about lookupTarget
fix fuzzy lookup on bilingual TMs

lookupTarget was taken to mean _only_ target in 42b750e, which is not the
intent.  This made testFuzzyLookupTargetOnlySearchesTargets pass, but not
for the right reason.  In fact, the test was failing because bilingual fuzzy
search was not taking keyLocale into account, so would find "A" in a
different locale.

This commit reverts 42b750e, takes keyLocale into account, and makes the
test more thorough regarding keyLocale and lookupTarget (and changes the
name).