XrdCl: Calculate the TPC tokens at the time when the copy process can actually proceed

This makes recursive third party copies possible.
XrdApps: Add --parallel to xrdcp commandline params
XrdCl: properly check if a recursive copy was requested
RPM: use common selinux policy building tools
RPM: Add systemd configuration files
RPM: Package the systemd scripts
RPM: Require expect
Logrotate: Prevent from hanging when trying to write to a dead-end pipe
Logrotate: Don't email or create new logfile after rotation. Fixes #135.
Set keepalive as the default socket value.
Add additional options to xrd.network to control keepalive option.
Update notes egarding keepalive setting change.
Logrotate: make selinux allow expect to access pseudoterminals and tmpfs
XrdCl: Make sure that the kXR_authmore data is sent.

This fixes an issue introduced in:

8b2a9dc9 XrdCl: Send kXR_endsess when reconnecting a channel
Build: Shorten the version extracted from git to be at most 25 characters
Build: Make the version shortening code simpler
XrdCl: Properly allocate a buffer for the error message. Fixes #136.
XrdCl: Discard a whole cluster on failure in federation context. Fixes #132.
XrdCl: Avoid inserting duplicate entries to HostList when retrying at the same server
XrdCl: Implement Utils::NormalizeChecksum
XrdCl: Normalize checksums before comparing. Fixes #139.