library improvement: ANTLR2 to ANTLR4

[duttonw]

This is in relation to getting seam java 11 happy

• remove org.codehaus.mojo:antlr-maven-plugin:2.2
• Update antlr:antlr:2.7.6 to org.antlr:antlr4:4.7.2
• Upgrade source files from antlr v2 to antlr v4:
  jboss-seam/src/main/antlr/org/jboss/seam/text/seam-text.g
  to (rename to g4)
  jboss-seam/src/main/antlr/org/jboss/seam/text/seam-text.g4
  change from v2 code style to v3 to v4.
• Test

related items:
Migrating from ANTLR 3 to ANTLR 4
Migrating from ANTLR 2 to ANTLR 3
https://github.com/magsilva/antlr-v2-to-v3
processing/processing#3055

[albfernandez]

I've removed the maven plugin, now the source java file should be generated outside maven, and added to git tree.
This way we can test on IDE easily (important for testing after migrate to v4).

I've implemented some basic tests copied from seam documentation.