license checker

Compares all source files against regular expressions for licenses and creates a file structure with files named after licenses that contain a list of files that apply to the respective license. E.g:
```
$ ./check.sh
$ wc -l out/*
    2 out/1c-BSD
   11 out/1c-BSD-ccnl
   12 out/1c-BSD-embunit
    2 out/1c-BSD-isc
    1 out/2c-BSD-v1
    2 out/3c-BSD-atmel
    1 out/3c-BSD-clark
   26 out/3c-BSD-openbsd
    3 out/3c-BSD-ti
    1 out/3c-BSD-v1
    4 out/3c-BSD-v2
    1 out/chan
    0 out/gplv2-short-v1
   10 out/gplv2-v1
    0 out/gplv3-short-v1
    0 out/gplv3-v1
    0 out/gplv3-v2
    0 out/lgpl-short-broken-grammar
  192 out/lgpl-short-riot
    5 out/lgplv2.1-v1
   33 out/lgplv2-short-v1
   25 out/lgplv2-short-v2
   16 out/lgplv2-short-v3
    1 out/publicdomain-v1
    8 out/unknown
  356 total
$ cat out/publicdomain-v1 
boards/msba2-common/tools/src/pseudoterm.c
```