[refactor] do some works

- move gitignore in individual directories.
- change some directory layout.
- refactor NlpCodec but not finished.

NlpParser/.gitignore

@@ -0,0 +1,42 @@
+# ===== Custom =====
+# Only preserve testbench in assets.
+assets/*
+!assets/testbench.txt
+
+# ===== ANTLR Output =====
+*.interp
+*.tokens
+
+Nlp*.java
+
+# ===== Eclipse Java =====
+# Eclipse projects
+.classpath
+.project
+.settings/
+.metadata
+
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+replay_pid*