Add new string modifiers base64 & base64wide based on the latest YARA release 4.0.0

Add snippets for imports
Add auto comments

Refactoring with the new syntax
Add snippets
Fix syntax highlighting bugs
Add test file for syntax

Fix syntax highlight between double quotes when there is an escaped double quote inside.
Add Comments Preferences allowing to use ST shortcut to toggle comments.
Update rule snippet.
Replace by tmLanguage by sublime-syntax (new syntax definition format).

Change the repo name according to https://packagecontrol.io/docs/submitting_a_package#Step_2

Update README
Add license
Change repo name