Disk free space reporting: 1. Enhance FileInfo:FileSize() to handle gigabytes and rename it to FileInfo:FormatSize() as it is not just for file sizes. 2. Add "Free space" field to file info because it is useful to see it when deciding whether to remove this file or not.
Disk free space reporting:
1. Enhance FileInfo:FileSize() to handle gigabytes and rename it to FileInfo:FormatSize() as it is not just for file sizes.
2. Add "Free space" field to file info because it is useful to see it when deciding whether to remove this file or not.

Conflicts:

	fileinfo.lua

Hzj-jie/koreader-base,apletnev/koreader-base,apletnev/koreader-base,poire-z/koreader,Frenzie/koreader,Hzj-jie/koreader,Frenzie/koreader-base,koreader/koreader-base,koreader/koreader,noname007/koreader,NiLuJe/koreader-base,frankyifei/koreader-base,ashang/koreader,frankyifei/koreader-base,NiLuJe/koreader,pazos/koreader,ashhher3/koreader,chihyang/koreader,mwoz123/koreader,Frenzie/koreader-base,NiLuJe/koreader,Frenzie/koreader,houqp/koreader,Markismus/koreader,Frenzie/koreader-base,koreader/koreader-base,poire-z/koreader,apletnev/koreader-base,koreader/koreader,Hzj-jie/koreader-base,houqp/koreader-base,Frenzie/koreader-base,NiLuJe/koreader-base,frankyifei/koreader,koreader/koreader-base,apletnev/koreader,koreader/koreader-base,NiLuJe/koreader-base,frankyifei/koreader-base,chrox/koreader,NiLuJe/koreader-base,lgeek/koreader,robert00s/koreader,Hzj-jie/koreader-base,frankyifei/koreader-base,houqp/koreader-base,NickSavage/koreader,houqp/koreader-base,mihailim/koreader,houqp/koreader-base,apletnev/koreader-base,Hzj-jie/koreader-base