misc: unify terminology

A(n) [type] error occurred while [attempting to] {verb} {noun}.
{cannot, can not, can't, could not} → unable to
has occurred →  occurred while
get → fetch
occured (typo) → occurred
serialisation (en-GB) → serialization (en-US)
serialised (en-GB) → serialized (en-US)
serialising (en-GB) → serializing (en-US)
succesfully (typo) → successfully
Successfully {adjective} {noun}. → {Noun} {adjective} successfully.
trial → attempt → while
tried to → attempted to → while
trying to → attempting to → while
users's (typo) → user's (singular possessive)

Change-Id: I1ca68038b17b0e8c4331c63de94b08ea4e097b20
GitLab: jami-client-qt#1730