update mkdocs packages versions, and improve info from xrootd_rpms

docs/site/xrootd_rpms.md

@@ -32,7 +32,7 @@ The following documentation describes how to install XRootD using RPMs.
     ```
 
 !!! info "Updating from XRootD v4 to v5 case"
-    Because of configuration fixes and not only the minimum version recommended is 5.1  
+    Because of configuration fixes and not only the minimum version is 5.1 (but recommended to use latest version available)
     See upgrading below
 
 
@@ -43,13 +43,13 @@ The following documentation describes how to install XRootD using RPMs.
     ~# yum -y install alicexrdplugins
     ```
 
-    3.2 For upgrade case it's best to remove all XRootD packages
+    3.2 For upgrade from v4 case it's best to remove all XRootD packages
 
     ```bash
     ~# yum remove -y xrootd*
     ```
 
-    Then one can install either the epel version or the upstream XRootD version
+    Then one can install either the epel version or the upstream XRootD version (N.B.!! epel have no downgrade path)
     <br>(see Yum repositories section from [XRootD downloads](https://xrootd.slac.stanford.edu/dload.html))
     ```bash
     ~# yum install -y xrootd-client xrootd-server
@@ -61,8 +61,8 @@ The following documentation describes how to install XRootD using RPMs.
         - `xrootd-aggregatingname2name` (dependent on XRootD)  
         - `alicexrdplugins` (metapackage, will pull all required dependencies)  
 
-    In special cases (when a test/preview is desired), `xrootd-alicetokenacc`, `xrootd-aggregatingname2name`, `alicexrdplugins` can be downloaded from [here](https://asevcenc.web.cern.ch/asevcenc/xrootd5alice/)
-    otherwise they are usually found in WLCG repository.
+    Until these pluggins are accepted in WLCG repository, `xrootd-alicetokenacc`, `xrootd-aggregatingname2name`, `alicexrdplugins` can be downloaded from [here](https://asevcenc.web.cern.ch/asevcenc/xrootd5alice/)
+    otherwise they are usually found in WLCG repository. (chose the relevant distro, for centos 7, chose `el7` directory.)
 
 
 ## XRootD Management Script