CACHE parameter* == CACHE=cacheControl[,cacheControl]*[:connMap]
cacheControl == do | no | ro
connMap == ProtoList[:[dstHostList][:srcHostList]]
-- default: none
-- restriction: applicable to HTTP, FTP, NNTP and Gopher
Specify a restriction of cache usage.
do -- create CACHEDIR if not exist (to enable cache)
no -- disable cache
ro -- use cache in read-only
Cache is enabled by default.
Cache will be disabled if the CACHEDIR directory does not exist,
or it is not readable and writable by the DeleGate,
or CACHE="no" is specified,
or "cache" is not included in CONNECT.