Wrap ChamplainFileCache

	* champlain/champlainmm.h: Add file-cache.h.
	* champlain/champlainmm/.gitignore: Ignore file-cache.*.
	* champlain/src/champlain_signals.defs: Add ChamplainFileCache
	"size-limit" and "cache-dir" properties.
	* champlain/src/filelist.am: Add file-cache.hg.
	* champlain/src/file-cache.[ccg|hg]: New files.
	* tools/extradefs/generate_extra_defs_libchamplain.cc: Add
	CHAMPLAIN_TYPE_FILE_CACHE.