[WIN32] fixed: don't copy skins via BuildSetup.bat. They're provided via their own build.bat
[WIN32] remove build_setup directory before the first git command to avoid problems with possible .git files.
Merge pull request #4004 from wsoltys/buildsys2

[WIN32] buildsystem fixes
json-rpc: return "lastmodified" in database datetime format (fixes #14836)
jsonrpc: fix setting/updating resume point in VideoLibrary