fix(instant): fix possible npe in case of filters with undefineds

solves #368
Merge pull request #369 from knalli/bugfix/instant-with-undefined-values

fix(instant): fix possible npe in case of filters with undefineds
fix(refresh): fix bug in refresh if using partial loader
fix($translate): Ensuring that languages will be set based on the order they are requested, not the order the responses come in.
fix($translate): Ensuring that languages will be set based on the order they are requested, not the order the responses come in.
fix($translate): Ensuring that languages will be set based on the order they are requested, not the order the responses come in.
docs(guide/en): Introduce Migration guide chapter

A new version of the Migration guide chapter. Here are listed important notes regarding
an application updating from one version to another.

Fix an error in the Migration guide chapter: You have to call `preferredLanguage` or
`use` method to make it work.
  docs(guide/en): Introduce Migration guide chapter
  fix($translate): Ensuring that languages will be set based on the order they are requested, not the order the responses come in.