app: introduce the GetAppByName function

Related to #696.
provision/docker: remove dump.rdb

wtf
app: use GetAppByName instead of App.Get

Also deleting the method.

Related to #696.
service/bind: fix tests that used App.Get

Related to #696.
api: use app.GetAppByName instead of App.Get()

Related to #696.
collector: use app.GetAppByName instead of App.Get()

Related to #696.
provision/docker: use app.GetAppByName instead of App.Get()

Related to #696.
all: rename app.GetAppByName to app.GetByName

Closes #696.