Resolve #161 and #162 | Misc
common-utils.sh: Fix _json_escape function for OSX sed
Add new flag --check-mode/-cm
Additional flag for --overwrite and --skip-duplicates flag. Can be used to change check mode in those flags, available args are 'size' and 'md5'.
There should be three modes:
name
name and size
name and md5sum
Default mode for skipping duplicates: name and size
Default mode for overwrite: name
Apply some fixes to install.sh