Delete some obsolete code.
"log-view" => "gdp-log-view".
First cut at external => internal name mapping using MySQL. It is
currently not an error if the mapping doesn't exist --- it just falls
back to the old SHA256 behavior --- and there is no automated addition
of the mapping to the database when you create a log. To make this work...
The grand renaming: GCL is (mostly) gone in favor of GOB and GIN.
Update .gitignore to skip another binary.
Add apps/gdp-log-check. This also substantially refactors
gdplogd/logd_disklog.[ch] so functions can be reused.
Add log-exists application. Also cleans up Makefile syntax to use
implicit rules properly.
Add gcl-clone command for Kaz's work on replication.
Add gdp-find-xname app to look up the external ID in log metadata.
Added gdp-extent to .gitignore
Rename "extents" to be "segments" because of different potential
semantics and enable them by default.
Clean up .gitignore files to make it easier to move things around (some
may be breaking out into separate projects).