Cake --boostrap should uninstall and/or use same as specified in #module directive

I updated a script from
```
#module nuget:?package=Cake.DotNetTool.Module&version=0.1.0
```
to
```
#module nuget:?package=Cake.DotNetTool.Module&version=0.2.0
```

`--bootstrap` installed the new version of the module, but the old one is still there

```
tools\modules
+---Cake.DotNetTool.Module.0.1.0
| \---lib
| \---netstandard2.0
\---Cake.DotNetTool.Module.0.2.0
\---lib
\---netstandard2.0
```

and the old being loaded and warnings still present even new available
```diff
- The assembly 'Cake.DotNetTool.Module, Version=0.1.0.0, Culture=neutral, PublicKeyToken=null'
- is referencing an older version of Cake.Core (0.30.0).
- For best compatibility it should target Cake.Core version 0.33.0.
- Could not load module - '/tools/Modules/Cake.DotNetTool.Module.0.2.0/lib/netstandard2.0/Cake.DotNetTool.Module.dll'.
```

Expected behavior would be to load the new version.

Possible solutions would be to uninstall versions that don't match during bootstrap, load latest version of each module, find a way for assembly scanning to pick specified version.

@cake-build/cake-team thoughts?