Create update.bat to sync windows binaries

[Kieran P]

With our move to git, we will be removing pyrogenesis.exe, pyrogenesis.pdb, and AtlasUI.dll (these three get generated by the autobuilder). As a result, we need an update.bat, or update.exe (whichever is easier) for windows users which can pull the latest binaries.

(quick background, the autobuilder will generate binaries for different code branches, and when its done, it will commit an updated manifest.txt file into the branch the binaries relate to, which points to the latest files)

• Use the manifest.txt file in the 0 A.D. code repo (probably stored at binaries/system), which contains a list of files, an md5 checksum for each file, and a url to download them from. Here is an example manifest:

AtlasUI.dll 52fe3f8c2725445b488f646dca28021f http://.../AtlasUI.dll
pyrogenesis.exe 89158e5ea74d5987ed8be026e7f090ce http://.../pyrogenesis.exe
pyrogenesis.pdb 44889d0fbf2f48972992c2a4d9e629c2 http://.../pyrogenesis.pdb

• Compare the manifest with the md5 of the current files. If no current file, download it. If existing file exists, find out if checksum has changed, and download the file if different.

• Once a file is downloaded, check file downloaded properly by comparing the files checksum with the checksum of the manifest.

This will allow us to easily add files in the future if need be (i.e. additional windows binary/dlls) and allows artists quick access to pull the latest binaries.