Fix License shown on github.com/finos/datahelix page

[maoo]

For some reason, GitHub tries to parse license-check.sh file as license, and therefore it doesn't recognize Apache 2.0 as the license (see screenshot.

)

Changing the filename (and updating the LICENSE file) seems to solve the issue (here's a screenshot of my fork (https://github.com/maoo/datahelix-2)

Note that the issue is also present in https://landscape.finos.org/