Merge pull request #90 from kwvanderlinde/bugfix/82-empty-function-calls

Support empty function calls and be more particular about successful parses

Replace antlr2 grammer with antlr4

The lexer is essentially unchanged, just tweaked to satisfy antlr4 expectations. The order of rules was modified for
readability, but is functionally the same.

The parser was subtantially changed, both to satisfy antlr4 as well as to take advantage of the new LL(*) capabilities.

There is a new strongly-typed AST as antlr4 does not provide its own AST. The parser test cases had to have minor tweaks
made to account for the differences:
- there is no more distinction between single- and double-quoted strings internally
- hex-coded integers are now the same as all other integers internally
- unicode strings are now supported

Meanwhile, all evaluation tests cases remain valid, and new multibyte unicode cases have been added.

Reformat lexer

Remove unused tokens, QUOTE and DID

Merge pull request #50 from cwisniew/fix-for-tru-fal

Changes so variables starting with tru / fal will no longer fail

Merge pull request #45 from nmeier/caching

Refactor Parser to separate expression parsing from evaluation.

Merge pull request #42 from nmeier/develop

Make +, ==, !=, eqs, neqs work for non-string/bigdecimal arguments

Merge pull request #37 from nmeier/develop

Add support for logical operators to Expression.format()/InlineTreeFormatter

Merge pull request #31 from Merudo/master

Add support for ISO-8859-1 characters

Merge pull request #28 from RPTools/develop

Merge pull request #28 from RPTools/develop

Develop (#6)

* Fix for generation of source java from antlr source (#5)

* Update build.gradle

Remove self dependency