intel 2015xe

Update the ictce toolchain to intel 2015xe and impi 5.

I've bumped the version to 7.0.0 for ictce.
this version number leaves very little freedom for downgrading, e.g. combining the 2015 compilers with impi 4.x

so, maybe use something like `7.1.2` (after you've bumped impi to 5.0.1)?