[api] move code around in statushistory to make the functions less complex
[api] move all patchinfo specific code into a patchinfo model
[api] move all attribute handling from source to attribute controller

(where it should have lived from the start)
[api] improve the patchinfo class a bit
[api] move issue rendering out of the models into views
[api] move rendering of configuration xml into a view
[api] move common relationship related functions into a mixin
[api] move rendering of project and package meta into a view
[api] move even more duplicated relationships code into the mixin