HPCC-8528 Create/remove symbolic links with during install/uninstall of clienttools

The fix includes followings:
1) A new directory clienttools under the top of source tree. It seperates install
   related scripts from Platform.
2) A new script: /opt/HPCCSystems/<version>/clienttools/etc/init.d/install/post_install.sh
   It will create the symbolic links of binaries (the list is hard-coded in the script) under
   clienttools/bin in /usr/bin.
   Run it with "-u" will remove the links if they belong to current version of clienttools
   The script should be run as user root.
3) If HPCC-Platform does not exist new clienttools install will create the symbolic
   links with script post_inrtall.sh
4) When uninstall a clienttools symbolic links will be removed with "post_install.sh -u"
   It only remove the link if it points to the file under current clienttools/bin/.
5) After clienttools uninstall, if there are still other clienttools left and not HPCC-Platform
   installed, it is user's responsibility to manually pick a clienttools and run post_install.sh
   if it exists.
6) this fix does not depends HPCC-9723 fix. But tests are assume HPCC-9723 included
   Test result matrix is attached in JIRA ticket HPCC-8528