Add .gitignore and .gitreview

Bug: 54175
Change-Id: Ic900b6a1aa3848aa59b428adef19115a9c55ac61
+ completed .gitignore
fix bug 52324: do not try to remap mime types for redirects or other types, which do not have a mime type
Added zimdiff class.
Fixed warning for zimdiff
Added zimpatch class to zimlib.
Added zimdiff and zimpatch binaries to zimlib
startfileuid and endfileuid are now stored properly. They can be read directly, without any transformation
Merge branch 'master' of https://github.com/kiranmathewkoshy/openzim
Merge with upstream