Enable auto convert when check in (apache#1926)

Leverage gitattributes to enable auto convert end-of-line to LF when
checking in. Convert already exist CRLF to LF by removing all files and
checking out with new .gitattributes file. Except .gitattributes, all
files are only modified at the end of line.

.gitattributes

@@ -0,0 +1,16 @@
+# Use whitelist to set text on
+# text means convert to LF when check in
+# eol=lf means convert to LF when check out
+*.cpp text eol=lf
+*.cc text eol=lf
+*.c text eol=lf
+*.h text eol=lf
+*.java text eol=lf
+*.py text eol=lf
+*.js text eol=lf
+*.md text eol=lf
+*.txt text eol=lf
+*.sh text eol=lf
+*.thrift text eol=lf
+*.proto text eol=lf
+*.conf text eol=lf