refactor by replacing cherly/dcerl with leo_mcerl/leo_dcerl AND fix bugs related to benchmark. close leo-project/leofs#69, close leo-project/leofs#68
fix invoking cmake only once
modify I/Fs to allow caller to use file:sendfile
fix bug not handling not_found
Update version of leo_mcerl and leo_dcerl
Format codes
Update for 0.4.5
Roll leo_cache version 0.4.5
Merge branch 'release/0.4.5'