Decide how to handle Database and Tool models - then implement them

[joncison]

These are both currently defined here as subclass of Resource, but it's unclear how to model them: the bio.tools API already handles databases and tools and we should re-use this so far as possible (an implementation of a database and tool model in the IFB catalogue may not be necessary, or perhaps just a simple one that leverages the bio.tools API).

[joncison]

From discussions with @hmenager - need to settle on a short list of attributes for databases and tools (could be one, or two different lists) which would be a subset of what's available in bio.tools. This is to support search over this content.

[bryan-brancotte]

Tool is down, model is ongoing with #228 #239