Allow basho_bench to pre-compute and pre-load Riak vnode data dirs.

Currently this only works with the eleveldb driver.  For maximum
utility, it should be extended to work with bitcask and other
Riak backends.
Add comments to examples/shortcut.config
Add support for Bitcask

Test method:

* Use the `examples/shortcut.config` file as shown to pre-populate 50K keys.
  Change the `code_paths` and `shortcut_data_dir` to reflect your
  environment.
* Run `./basho_bench ./examples/shortcut.config`
* Over on a Riak console, use:
  * {ok, C} = riak:local_client().
  * [ok] = lists:usort([catch element(1, C:get(<<"b1">>, <<X:32/native>>)) || X <- lists:seq(0,49999)]).
Add support for experimental hanoidb storage manager
Refactor preflist calculation, clean up debugging cruft
Add base64, concat_binary, and as-is-binary key generators

New key generators:

* {base64, BinaryGenerator} will Base64-encode the binary created
  by BinaryGenerator.
* {concat_binary, GenOne, GenTwo} will concatenate the binaries
  created by the GenOne and GenTwo generators.
* Any literal binary B will create a fixed binary generator that
  always generates B.
Add example config that uses concat_binary & base64 key generators
verify seq_int resume value is not out of bounds
add delete support for basho_bench_driver_http_raw
Merge pull request #50 from basho/slf-string-key-generator-additions

Slf string key generator additions
Merge pull request #71 from basho/sbv-add-raw-http-delete

add delete support for basho_bench_driver_http_raw
Fix incorrect error case clauses
Merge pull request #73 from basho/eas-fix-err-case-clauses

Fix incorrect error case clauses
Remove non-source file from src dir
Add uniform_int start/#keys generator

I needed this when testing a 2i problem that involved only big integers.
Merge pull request #74 from basho/eas-add-uniform-int-range

Add uniform_int start/#keys generator
Add additional configuration items to basho_bench_driver_riakc_pb.erl

* pb_connect_options, list(two_tuple()), list of valid Protocol Buffers
  client connection options.
  Default = [{auto_reconnect, true}]

NOTE: The new default value creates a change in behavior of the
      PB client: the default is {auto_reconnect, false}.  Users
      of the PB client that wish the old & brittle behavior of
      crashing on server-side errors, timeouts, etc. must provide
      explicit configuration now to disable auto_reconnect behavior.

* pb_timeout_general, integer(), overall single Protocol Buffer
  operation timeout value.
  Default = 62000
  Units = milliseconds

* pb_timeout_read, integer(), overall single Protocol Buffer
  read operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_write, integer(), overall single Protocol Buffer
  write operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_listkeys, integer(), overall single Protocol Buffer
  listkeys operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds

* pb_timeout_mapreduce, integer(), overall single Protocol Buffer
  mapreduce operation timeout value.
  Default = value of pb_timeout_general
  Units = milliseconds
Fix partitioned seq int gen leaving some keys out

Fixes #75
For example, with 12 workers and 100 keys, it leaves the 4 last keys out
(100 rem 12).  This makes those keys (at most # of workers) be given to
the last worker.
Merge pull request #76 from basho/eas-fix-remainder-partitioned-seq-int

Fix partitioned seq int gen leaving some keys out
Merge of branch  slf-bulk-insert-shortcut2