Re-implement watcher.py using low-level kazoo watchers.

AS explained in DM-513 the threads that were started by the previous
version of the script did not make much sense so they were removed.
High-level wather class ChildrenWatch has issues when "root" node is
deleted. To workaround this issue high-level watchers were replaced
with low-level watchers (callables passed to get(), exists(), or
get_children()). One additional watcher was introduced to restart
"children" watcher when root node is re-created.

Even with all above changes there is still a potentially serious
issue with missing updates to zookeeper nodes. It is inherent to
one-shot zookeeper/kazoo watchers and I do not see a way to fix it.
Merge branch 'u/salnikov/DM-513'
Qserv build on Ubuntu 14.04 requires specific gcc flags.

This issue is encoutered using GNU ld (GNU Binutils for Ubuntu) 2.24.

In gcc command lines:
  * for testIter and testQservOss build: -lpthread added
  * for testProtoRowBuffer build: -lcrypto must be in last position
Install directory option (-i) of automated install script supports symbolic links
Update in automated install script related to DM-1287 (QSERV_DIR/admin was removed for in-place install)
Fix error introduced by editor wrap problem

Emergency fix.
Improve cleaning prior to automated install

Emergency fix. In automated install script,
prior to stack install, hidden files and directories
are now also removed.
Use of LD_LIBRARY_PATH in etc/init.d/xrootd

Path to Qserv plugin is no more hard-coded in
xrootd configuration file, but infered using
LD_LIBRARY_PATH.
Use of QSERV_LUA_SHARE in etc/init.d/mysql-proxy

QSERV_LUA_SHARE relies on LUA_DIR and points to
lua libraries path. It has been moved from mysql-proxy
configuration file to an environment variable in service
startup script.
Remove Qserv install directory from qserv-client.conf
Compute lua library paths in etc/init.d/mysql-proxy

Computation of lua shared and libraries directories, using lua install
directory (i.e. LUA_DIR), moved from configuration procedure to
mysql-proxy init.d script. This will allows mysql-proxy to use eups
LUA_DIR environment variable, without having to re-configure Qserv.
Enable use of eups environment in etc/init.d/qserv-czar

- move init.d script configuration parameters issued from meta-config
  to etc/sysconfig/qserv-czar
- if EUPS_DIR environment variable exists, then etc/init.d/qserv-function
  loads eups environment, instead of the one issued from meta-config file.
Add of meta-config file location in template parameters

Header comments of template-generated files can display
used meta-configuration file.
Enable use of eups environment in etc/init.d/mysql-proxy
Enable use of eups environment in etc/init.d/xrootd
Separate paths management for Qserv services

- init.d/path.cfg.sh loads paths in environment using eups or
  meta-config file,
- source_sysconfig() loads parameters for Qserv services
  from etc/sysconfig/service-name.
Enable use of eups environment in etc/init.d/mysqld
Enable use of eups environment in etc/init.d/zookeeper
Improve one configuration error message
Group paths and parameters management for services

init.d/path.cfg.sh is now sourced in source_sysconfig(),
in order to slim init.d script and ease maintenance.