new module: sysctl to handle sysctl entry

sysctl now capable to search for sys entry into /sys if not under /proc/sys

module/sysctl rolling back to 0.5

write sysctl.conf safely, tempfile first, atomic replace after.
See comments in  https://github.com/ansible/ansible/pull/1810

Patch to replace .format with % () to handle python-2.4 ,
See also https://github.com/ansible/ansible/pull/1810

using name instead key for default arg name. key putted as alias.
also, val become an alias of value arg name.
See also : https://github.com/ansible/ansible/pull/1810