Add Moved(GB) to Compaction IO stats

Summary:
Adds counter for bytes moved (files pushed down a level rather than compacted) to compaction
IO stats as Moved(GB). From the output removed these infrequently used columns: RW-Amp, Rn(cnt), Rnp1(cnt),
Wnp1(cnt), Wnew(cnt).
Example old output:
Level   Files   Size(MB) Score Read(GB)  Rn(GB) Rnp1(GB) Write(GB) Wnew(GB) RW-Amp W-Amp Rd(MB/s) Wr(MB/s)  Rn(cnt) Rnp1(cnt) Wnp1(cnt) Wnew(cnt)  Comp(sec) Comp(cnt) Avg(sec) Stall(sec) Stall(cnt) Avg(ms) RecordIn RecordDrop
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  L0     0/0          0   0.0      0.0     0.0      0.0    2130.8   2130.8    0.0   0.0      0.0    109.1        0         0         0         0      20002     25068    0.798      28.75     182059    0.16       0          0
  L1   142/0        509   1.0   4618.5  2036.5   2582.0    4602.1   2020.2    4.5   2.3     88.5     88.1    24220    701246   1215528    514282      53466      4229   12.643       0.00          0    0.002032745988  300688729

Example new output:
Level   Files   Size(MB) Score Read(GB)  Rn(GB) Rnp1(GB) Write(GB) Wnew(GB) Moved(GB) W-Amp Rd(MB/s) Wr(MB/s) Comp(sec) Comp(cnt) Avg(sec) Stall(sec) Stall(cnt) Avg(ms)     RecordIn   RecordDrop
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  L0     7/0         13   1.8      0.0     0.0      0.0       0.6      0.6       0.0   0.0      0.0     14.7        44       353    0.124       0.03        626    0.05            0            0
  L1     9/0         16   1.6      0.0     0.0      0.0       0.0      0.0       0.6   0.0      0.0      0.0         0         0    0.000       0.00          0    0.00            0            0

Task ID: #

Blame Rev:

Test Plan:
make check, run db_bench --fillseq --stats_per_interval --stats_interval and look at output

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D29787