Remove Zotero.Browser and add HiddenBrowser.jsm. Post-Fission, web/file
content loads in a separate process, so it's not possible (as best as I
can tell) to directly access the contents of a hidden browser -- it just
appears as about:blank in the parent process. We now use Mozilla's
JSWindowActor mechanism [1] to get page data, including character set
and body text for full-text indexing. We'll have to evaluate other uses
of hidden browsers to see how to handle them.
This also adds include.jsm for loading the Zotero object into a JSM.
[1] https://firefox-source-docs.mozilla.org/dom/ipc/jsactors.html
Restore prepopulated charset table, but this time with just the
encodings from the WHATWG Encoding Standard. Assigning a charset to
Zotero.Item::attachmentCharset runs the value through
Zotero.CharacterSets.toCanonical() automatically.
This migrates attachment charsets to the new canonical values, clearing any
that are unsupported.
Other legacy mappings could still be added back, as disussed in #760.
