Added Slabv1 specific RSpec support.

Added Slabv1 specific RSpec support.
Added special Timeslot element files.
Timeslot supports specification of different timezones
when creating a new experiment using senslab Rspec, computed
in AddSliceToNodes.
Timeslot format used :
<timeslot time="2012-04-26 10:00:00 Canada/Central" duration = "00:18:45" />
Timeslot does not belong to Node element, nor Sliver element.
Specific xml header should be used in order to trigger Slabv1 rspec
parsing functions.
<?xml version="1.0"?>
<rspec type="request" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://senslab.info/resources/rspec/1" xmlns:flack="http://senslab.info/resources/rspec/ext/flack/1" xmlns:planetlab="http://www.planet-lab.org/resources/sfa/ext/planetlab/1" xsi:schemaLocation="http://senslab.info/resources/rspec/1 http://senslab.info/resources/rspec/1/request.xsd http://www.planet-lab.org/resources/sfa/ext/planetlab/1 http://www.planet-lab.org/resources/sfa/ext/planetlab/1/planetlab.xsd" expires="2012-04-20T09:43:07Z" generated="2012-04-20T08:43:07Z">