feature #2371: add pagination to pool info

When the end_id of pool.info xmlrpc call is lower than -1 the parameters
do not refer to object ids but offset and cuantity used for pool pagination.r
The SQL query will have "LIMIT start_id,-end_id".
feature #2371: add pagination to ruby oca, cli and sunstone

There is a new pool method called get_hash that uses pagination when possible.

The default page size can be changed with the environment variable
ONE_POOL_PAGE_SIZE. Any value > 2 will set a page size, a non
numeric value disables pagination.

Paginated pools are parsed using sax instead of dom so this makes the parse
a bit faster. It will also detect Ox gem (https://github.com/ohler55/ox) and
will use it as it is much faster than Nokogiri.

Screen cleaning in top command is done after retrieving the pool reducing
the flickering.
feature #2371: add ox gem to install_gems
feature #2371: delete debuging STDERR.puts
bug #2657: fix VMM driver to send one action per host

(cherry picked from commit 0eb00fc502cc0810a396c79440e235abed990573)
Merge branch 'feature-2371'