Updated README files to refer to usage of scons

Updated README files to refer to usage of scons

Changed README files in resource/csdk/connectivity/samples/linux/
and resource/csdk/stack/ directories to refer to usage of scons
instead of make commands.
Removed trailing whitspaces as well, as recommended from Erich
and also removed the references to sample.sh as per
https://gerrit.iotivity.org/gerrit/#/c/1253/

Change-Id: I9f61ea80c12b48f0a86ea4ff24e0758d288ddc8e
Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1254
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>