[conda-env/buildout] Minimize conda environment specification; Update python to 3.6; Use bob/beat-devel for specs; Remove sysegg recipe from buildout files

Fix mail handling

Closes #509

See merge request !260

Generic try except use were hiding errors due to Django documented
changes about the usage of Context with template rendering. This
patch updates the code to not use Context anymore and remove the
generic try except.

Fixes #509

Most email sending code follows the same logic, these helpers
allow to avoid all the code duplication.

The current message was stating Data format rather than the
actual model being used.

Fix database retrieval

See merge request !259

Getting the declaration through the property gives us an
ordered dict. This update also sends back a properly formatted
json document rather than a string.

This method is explicitly there for handling json answer

If a toolchain comes with empty connection representation data,
the editor and viewer will fail to load as they only check if the
information is available and are missing a check about its
emptiness.

Set schema_version to 2 if not provided

See merge request !258

This can happen when converting a v1 analyser.