Added debugging logs.
Added retry mechanism on the Put().
Fixed bug in use of munmap() -- wrong address.
Quick fix on the location storage.

The location is now tested to prevent concurrent writes on entries with
the same keys. This is only a temporary fix and should be replaced by
proper multiversion/ordering of events.
Replaced LOG_TRACE by LOG_EMERG on critical errors.
Increased the maximum number of open files.

Used RLIMIT_NOFILE to increase the maximum number of open files for the
process. This is necessary as the current version of the storage engine
is still opening a lot of files concurrently to access the data on
secondary storage.
Added option to disabled thread-safe mechanism in logging.
Added Vim swap files to .gitignore