Cache downloaded templates

[cbaakman]

Hommod needs to access template files (pdb structures) multiple times each modeling run. This can be with intervals of seconds.

Currently, hommod re-downloads the pdb structure with each new step that uses it. But I think it would be faster to have a pdb service in hommod that handles the request for a template file and downloads it only once per modeling run.

[jonblack]

A couple of questions:

1. Is the problem that this costs a lot of time? How much time are we talking about?
2. Where is the downloading done? Is this the calls to yasara.loadpdb?

[cbaakman]

1. The downloading takes several seconds, it can be called more than 20 times per run
2. The downloading is donw in yasara.LoadPDB, with the download option set to 'yes'

[jonblack]

We can wrap the yasara function in a cached function using dogpile.