merging all .gitignores into one

SSIA

Before:

```
[lzap@lzapx katello]$ g find gitignore
.gitignore
katello-utils/.gitignore
src/.gitignore
src/doc/graphs/.gitignore
```

After:

```
[lzap@lzapx katello]$ g find gitignore
.gitignore
```

Find three differences!