nimble init should auto-create "src/FOOpkg" dir for submodule instead of just "src/FOO"
## Current dir structure created by `nimble init FOO`

```
FOO/
├── FOO.nimble
├── src/
│  ├── FOO.nim
│  └── FOO/
└── tests/
   ├── config.nims
   └── test1.nim
```

## Problem

If I do `nim c -r src/FOO`, I get:

```
Hint: FOO [Processing]
Hint: macros [Processing]
/usr/bin/ld: cannot open output file /home/kmodi/sandbox/nim/FOO/src/FOO: Is a directory
collect2: error: ld returned 1 exit status
```

This is because on linux, you cannot have a binary **and** a directory named the same in the same directory. So you cannot have the FOO binary and FOO/ directory in the same place.

## Proposed auto-generated structure

Create `src/FOOpkg/` directory instead of `src/FOO/`.

```
FOO/
├── FOO.nimble
├── src/
│  ├── FOO.nim
│  └── FOOpkg/
└── tests/
   ├── config.nims
   └── test1.nim
```