Add XRegExp from https://github.com/slevithan/xregexp/tree/d06eff50f87d81d2dd3afc1e854784c38b17bcc4/src
Load XRegExp into Zotero.XRegExp and Zotero.Utilities.XRegExp and make it accessible from translators.
Remove unnecessary character classes. Add some useful ones.
Use 100 lines
Merge remote-tracking branch 'aurimasv/xregexp' into 3.0
Tweak loading process
Fix source files to be UTF-8
Merge pull request #231 from aurimasv/defaultHandlers

Set default handlers if they are not set
Use Zotero.wait() to move progress indicator

This may help with #230
Allow translators to define translator-specific hidden preferences.