Started the post-TPAC changes

- created a separate test suite
- the metadata files are now called via the new names. Note that the suffix is now '.json' and not '.csvm', i.e., jQuery parses the input into an object on the fly, no need for an explicit JSON parsing as before
Added the 'overriding metadata' feature
Changed the order of the metadata merge, but what exactly merge means seems to be way more complicated, now discussed on the WG
Tiny change in the README

In fact, experimenting with pull requests...
Merge commit 'b66e5e015f9c0b169a07510c7153dfdb22e8574e' into after-tpac
Merge branch 'after-tpac' into gh-pages