Change license from MIT to MPL 2.0

While the MIT license is a fantastic license for those too lazy (or
unable) to understand more complex licenses it's too lax when it comes
to protecting authors (= me). For example, there are no clauses regarding
patents or ownership of source code. This means that patent trolls
could, in theory, drag me to court.

Of course one can still do that when using the MPL, but at least it has
an explicit clause regarding patents. The MPL also provides a nice
balance between the MIT license and the Apache license. I don't like the
Apache license as it requires listing any significant changes in every
changed file.

In short, I don't really care what people do with my software (they
could sell it for millions for all I care), as long as they don't drag
me to court or otherwise hold me accountable for something.

doc/DCO.md

@@ -1,25 +0,0 @@
-# Developer's Certificate of Origin 1.0
-
-By making a contribution to this project, I certify that:
-
-1. The contribution was created in whole or in part by me and I
-   have the right to submit it under the open source license
-   indicated in the file LICENSE; or
-
-2. The contribution is based upon previous work that, to the best
-   of my knowledge, is covered under an appropriate open source
-   license and I have the right under that license to submit that
-   work with modifications, whether created in whole or in part
-   by me, under the same open source license (unless I am
-   permitted to submit under a different license), as indicated
-   in the file LICENSE; or
-
-3. The contribution was provided directly to me by some other
-   person who certified (1), (2) or (3) and I have not modified
-   it.
-
-4. I understand and agree that this project and the contribution
-   are public and that a record of the contribution (including all
-   personal information I submit with it, including my sign-off) is
-   maintained indefinitely and may be redistributed consistent with
-   this project or the open source license(s) involved.