merge 3.19.5 into 3.20 branch

Added tag cubicweb-version-3.19.5, cubicweb-debian-version-3.19.5-1, cubicweb-centos-version-3.19.5-1 for changeset 3ac86df519af

i18n update 4 strings have disappeared.

[pkg] 3.19.5

[server] hold connection to the db in tx_actions We can be called without a cnxset (e.g. from repoapi).

[wsgi] If multipart cannot parse the POST content, let it pass. multipart can only parse html form data. It the content_type is, for example, "application/json", get_posted_data should not fail but just stop trying to read the content. Closes #4421845

[devtools] Fix JS tests' HTML code

[devtools] "Keep" some temporary files/dirs around to help with debugging The whole QUnitTestCase runs with an @with_tempdir so it's redundant anyway.

[devtools] Fix Firefox launcher in QUnitTestCase (closes #4294727) The main changes are: - stop creating the profile, firefox will create it - point firefox to a profile directory instead of giving it a profile name (this has the added bonus of not polluting the user's profile list) - start firefox once and kill it 5 seconds later to let it finish its profile creation (along with system-wide extensions setup)

[devtools] allow cross-origin requests for qunit We have a mix of file:// html and http:// ajax calls. Which we should at some point fix to all be http, but. Related to #4294727.