Add database tasks for Rails 4.1

These are db tasks, using FreeTDS for dump and load tasks, as discussed in #334

Other than dump, everything seems to work fine. Dump has some issues, due to FreeTDS defncopy bugs.

Firstly, defncopy had a few syntax errors when dumping, these are substituted in structure_dump, so at least the dump is valid and can be subsequently loaded.

However, defncopy also does not seem to dump foreign keys - this cannot be trivially fixed, without rewriting the schema dumping functionality ourselves. There is a warning stating this when you do a structure dump.

Also, if you want to try it and have views defined, it is possible that you will need to download FreeTDS and compile it with this patch https://gitorious.org/freetds/freetds/merge_requests/29

What do you think?