[hotfix] pull in upstream merged mr 14

This brings our fork up to date with head of upstream master as of 2020-08-21.

It tracks signald as of this commit:

• https://gitlab.com/thefinn93/signald/-/commit/dd907ab1e39271d214ffaa7612009ae1b9fe4179

And incorporates all the changes in this significant MR (merged on 2020-08-14):

• https://gitlab.com/thefinn93/signald/-/merge_requests/14?commit_id=325297c366fa343e56d2086ff4ef8465dcd08915

New since last merge:

• a bandaid on file corruption issues
• some dependency updates
• different attachment string generation method
• tracks upstream update to Asamk's libsignalservice-java fork
• supresses some stack traces for bugs that we explicitly catch and print lower in the stack

--

cc @mari