Use alembic instead of sqlalchemy-migrate (fixes #219)

As sqlalchemy-migrate isn't actively developed anymore, it is
recommended to switch to alembic. Our previously used version of
sqlalchemy-migrate wasn't compatible with SQLAlchemy 0.8 and thus
prevents us from updating, and the latest version doesn't build with
buildout (see [0]). Therefore let's update now.

This commit
- installs alembic instead of sqlalchemy-migrate
- initializes an alembic environment below src/adhocracy/alembic
- adjusts the code which is called from `paster setup-app`
- leaves the old sqlalchemy-migrate migrations in place (for now; we
could probably also just remove them)

In order to migrate to alembic, we need to make sure users update to a
git tag (e.g. version 1.9) before this commit, perform their remaining
sqlalchemy-migrate migrations, and then move to this commit or newer and
start using alembic.

[0] https://code.google.com/p/sqlalchemy-
migrate/issues/detail?id=165&sort=-id
Add MutableList (required for SQLAlchemy >= 0.8)
Update SQLAlchemy (0.7.10 -> 0.9.1)
rm instance settings title
do not escape title definitions

When the definitions are used they will be escaped a second time

This commit is very incomplete
fix file upload in overlays

To include files in our upload this uses the FormData API.

Unfortunately, FormData is only available in IE 10+. In
older IEs, the whole form will be unusable.

To limit the damage this does only use FormData where necessary.
use FormData whenever available

This is an improvement because now forms with
enctype="multipart/form-data" will non break completely
on non-supporting browsers
add warning to ajax form submit for old browsers
abstract overlay.close
close overlays on esc (fixes #598)
fixup breadcrumbs
rm js tooltips (fixes #208)

The JavaScript tooltips we are using are buggy.

I see no real reason why we use the in the first place
because the tooltip implementation in browsers is quite good
and probably has benefits in terms of accessibility, too.

So this removes the js tooltips.
add .text as UGC
create proposal row_inline
refactor proposal code
add proposal text
add proposal comments route
Merge pull request #729 from xi/feature-598-fix-overlay-esc

fix overlay esc
Merge pull request #731 from xi/feature-208-rm-js-tooltips

rm js tooltips (fixes #208)
use overlay's native close()