Summary:
This allows ldb to control the write_buffer_size (which reflects to L0 file size) and file_size (which reflects to L1 file size). Since the target_file_size_ratio is 1 by default, all other levels will also have the same file size as L1.
As part of the diff, I also cleaned up some unused code and help messages.
Test Plan: ./ldb load --db=/data/users/zshao/test_leveldb --file_size=64000000 --write_buffer_size=32000000 --create_if_missing --input_hex --disable_wal
Reviewers: dhruba, sheki, emayanke
Reviewed By: dhruba
CC: leveldb
Differential Revision: https://reviews.facebook.net/D7569
70f0f50731