Update docs, add rsync timeout, verify mft existence.

Update docs, add rsync timeout, verify mft existence.

+Add missing dependency at some distros (libcurl) and update 'libxml' package (the '*-devel' package is required).
+Add '--timeout' parameter to rsync command, the default value is the same as 'http.idle-timeout' (15 secs). Update docs where this value is referred.
+Verify that the manifest file exists locally after downloading a repo, if the file doesn't exist, then the repo is discarded and (possibly) another repository will be utilized (eg. rrdp or rsync repo).