Release 0.1.9: Language improvements and fixes

Language changes:

• New functions min() and max() added
• New function hash-int added (thanks to @ecerulm)
• null + object now produces the object (not null)
• null + array now produces the array (not null)

API changes:

• FileSystemResourceResolver added (thanks to @ngsoftwaredev)
• Made it possible to configure encoding on resolvers

Bug fixes:

• Support leading zeroes in strings passed to number() (issue #112)
• Support Cyrillic characters in string literals (issue #115)
• Upgraded to Jackson 2.10.3 (security fixes)
• Handle null being returned from Java extension functions
• Avoid NullPointerException when statically wrapped method does not exist