I am using a Moto E. The apps I have downloaded and use are few, and they are not taking up much space. What can be moved to the SD card has been moved. Yet, I have only 256MB space available now. Question: is there a way to remove apps such as Motorola Migrate, Contextual Services etc etc, to free up space without affecting the overall operation of the phone? Can, for example, Google apps as Calendar be removed completely? Does the phone need to be rooted if this is possible?
Even if you could remove them, that wouldn't free up space in user-data (pre-installed apps are stored in a separate partition the user has no write-access to).
What you could do, however, is go to Settings › Apps, switch to the "All" tab, open the entry for each of those apps, and see if you can "uninstall updates" and then "disable" the app (to prevent those updates to come back). Other than the apps themselves, those updates are installed in user-space.