lwm2m_remove_object(...) return removed object

[parmi93]

Small change to the lwm2m_remove_object(...) function so that it returns the pointer to the removed object.

[parmi93]

Fixed the commit message according to the rules.

[parmi93]

Removed the history of commits, in order to be able to resolve errors related to commit messages that did not respect the rules.

[rettichschnidi]

When exactly will this be useful? Would be great to have this information also in the commit message.

[parmi93]

This parameter is never used inside the library, but in my case it is useful.
I developed an LwM2M client that allows the user to add and remove LwM2M resources on the fly.

Basically the user sends commands from a terminal to add, modify, and delete LwM2M resources, the parameter added through this PR is useful to me during the removal of a LwM2M resource, in this way once the resource has been removed from Wakamma lib I can perform the free of the pointer returned by 'lwm2m_remove_object(...)'