Refactor .gitignore into readable, intuitive format.
Refactor .gitignore into readable, intuitive format.

Previously, .gitignore was a raw dump of `git-svn show-ignore`. We are now
moving towards using git (coming soon!), so this makes the .gitignore more
manageable and concise. For now, there is a single top level .gitignore. It
might make sense to create a separate test/.gitignore in the future for all the
obscure test ignore rules.

r: kyle-b

git-svn-id: 88467cb1fb04b8a755be7e1ee1026be4190196ef@23468 3a8e244f-b0f2-452b-bcba-4c88e055c3ca

chizarlicious/chapel,hildeth/chapel,chizarlicious/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,sungeunchoi/chapel,hildeth/chapel,hildeth/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,chizarlicious/chapel,hildeth/chapel,chizarlicious/chapel,chizarlicious/chapel,chizarlicious/chapel,CoryMcCartan/chapel,chizarlicious/chapel,hildeth/chapel,CoryMcCartan/chapel,hildeth/chapel,hildeth/chapel,sungeunchoi/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,CoryMcCartan/chapel,sungeunchoi/chapel,CoryMcCartan/chapel