Improvements..

Hi ! thanks for this package, very handy. I was worried about "scanning the complete folders on save", and took a look.. started doing some small improvements and ended doing a lot, but basically keeps the same heart. Here a somewhat complete list:

- compile regular expressions at startup
- add preferences to exclude folders and files
- fix bug in regular expressions where in some situations more than the signature may be added
- enable to work on unsaved files, these that hint JavaScript syntax
- enabled in JavaScript scopes (eg in html 'script' tags)
- only crawl the saved file if it is a JavaScript file
- get signatures from all the windows
- get signatures from all the opened views
- simplifications
- on post save runs async
- parse opened files outside of this current project/folder only if it is not already indexed
- avoids duplicates files and folders added by project folders duplicating paths
- avoids duplicate signatures for the same file
- watch for folders changes
- only reparse files that have been modified

The major change is:
1. Folders are scanned only the first time these are seen.
2. Individual files are scanned when saving, and just that file