webserver: cosmetic refactoring
webserver: add support for If-Unmodified-Since HTTP header
webserver: add Cache-Control HTTP header to cacheable responses
webserver: handle Cache-Control: no-cache and Pragma: no-cache
webserver: use defines for HTTP header fields and values
webserver: silence warning
webserver: refactor IsAuthenticated()
[win32] remove non-existing header files from project files

Stops projects from always being built in VS when nothing changed.
[win32] git_revision custombuild trigger from existing file, set correct outputpath, remove non existing dependency.
[win32] remove redundant /MP compiler option in release builds.

The duplicate /MP option (listed in "Additional Options" and also enabled with the "Multi-processor Compilation" option) was causing a full rebuild because msbuild is removing the duplicate from the commandline causing:
"Forcing rebuild of all source files due to a change in the command line since the last build."
win32: fix indentations in BuildSetup.bat
win32: add nopvraddons and nobinaryaddons options to BuildSetup.bat
[infomanager] added Container(id).CurrentItem
[mediawindow] remove unused function OnFinalizeFileItems
FIX: [droid;packaging] handle addons libraries
FIX: [droid;python] proper handling of module libraries
FIX: [droid] make python PIL module working
[android] [vfs] PosixFile: fix large file support on Android
media library: fix path history for items with a real path differing from the requested path
[rebrand][German keyboardmap.xml] xbmc -> kodi