Add list of API changes in wiki

[dragly]

We have made a number of API changes from 0.4 to 1.0. These should be documented in the wiki. Some are breaking changes and some are deprecations that will be broken in 1.1 or later.

• A simple way to find all deprecations is to look for any mention of deprecation or any warnings in the diff.
• A simple way to find all breaking changes might be to use git diff 0.4..dev | grep def, which should list all function definitions that have changed.

[lepmik]

Is this still necessary when we move to the filesystem version? There are many breaks, and few users... @dragly